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Shopify development · Shopify Plus
Castle designs, builds, migrates and optimises Shopify and Shopify Plus stores for brands across the UK and beyond. Every build is measured on conversion rate, order value and revenue, not on launch day.
Why the build matters
Anyone can open a Shopify store in an afternoon. That is exactly why the stores that win are the ones built with more care than the theme next door.
There are 231,569 live Shopify stores in the UK (Store Leads, October 2026). A lightly edited theme looks and behaves like thousands of competitors, and gives shoppers no reason to stay.
Each app adds a monthly fee, extra scripts and another thing that can break. Stores we audit often carry apps for jobs the theme could do natively, faster and for free.
Shopify’s Spring ’26 Edition shipped 150+ updates centred on selling through ChatGPT, Copilot and Perplexity. Clean product data and a well-structured catalogue decide whether you show up.
What’s included
From the first wireframe to the hundredth A/B test: strategy, design, development, migration and ongoing optimisation by one in-house team, measured on what the store sells.
UX and UI designed around how your customers actually buy.
Measured on conversion rate
Online Store 2.0 themes, customised or coded from scratch.
Measured on Core Web Vitals
Enterprise features for brands that have outgrown standard Shopify.
Measured on revenue per session
Replatform from WooCommerce, Magento, BigCommerce or Wix safely.
Measured on organic traffic retained
More revenue from the traffic you already have.
Measured on conversion rate and AOV
The right apps, fewer of them, connected properly.
Measured on app spend and page weight
A fast store that search engines and AI shopping tools can read.
Measured on LCP and organic revenue
A team on hand after launch, not a handover and goodbye.
Measured on response time and release pace
Every build includes
Shopify results
Published results from Castle-built Shopify and Shopify Plus stores. Every figure links back to the full case study.
A global appliance brand. Our Shopify developers rebuilt the store to new brand guidelines, then Google and Meta campaigns were built around it.
A rebrand and bespoke Shopify Plus store. With paid ads restricted for CBD, the build had to convert: bundles, a slide cart and a free-gift threshold lifted order value by 6%.
A bespoke theme built for conversion: search, mega menu, filters and a slide cart with cross-sell upsells, followed by SEO, affiliate and Meta ads.
Client reviews
Castle took Supreme CBD to the next level with the new branding and website. They’ve increased the sites revenue by 86% in the first 3 months. …they’re really responsive and helpful and go above and beyond to deliver.
…the results have been outstanding. They’ve completely turned around our online performance — Google Ads are running more efficiently than ever, Meta campaigns are consistently profitable, and our Shopify sales have seen real, measurable growth month after month.
…Smashing targets & 24/7 support which is a big bonus for us can’t thank them enough. Connor who’s trying different strategies & believe me they bring in the results!
I honestly can't say how good everyone is at Castle, they can't do enough for you and the work and numbers they produce out of this world. If I could leave 10 stars I would
The whole team at Castle International are an absolute asset to any business that needs a positive boost in their marketing strategy. Expertise, knowledge, patience and a friendly helpful attitude, aiming to give you a bespoke service throughout.
Our business has benefited massively by Castle and their team of creative experts. It is a wonderful company that is always working to achieve the best for you. They have a wealth of knowledge and offer outstanding marketing solutions always ensuring they deliver on their promise
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Build options
There is no single right way to build a Shopify store. The right route depends on your catalogue, how your customers buy and how fast you need to move. We will tell you which one fits, including when the cheaper option is the right one.
A proven Online Store 2.0 theme, extended and restyled to your brand, with custom sections where the theme falls short.
Trade-off: you inherit the theme’s structure and code weight. Fine for most catalogues; limiting if the buying journey is unusual.
A theme designed in Figma and coded from scratch in Liquid for your products, your customers and your trading model. No unused code from someone else’s template.
Trade-off: a bigger upfront investment. Repaid when conversion rate and order value are the constraint, not traffic.
Shopify’s enterprise plan, or a headless storefront using Hydrogen, for high-volume brands that need checkout control, B2B, multiple markets or deep integrations.
Trade-off: higher platform fees and more moving parts. Headless only when the business case is clear; most Plus brands stay on a theme.
Timelines are typical ranges for a full build and depend on catalogue size, integrations, content readiness and how quickly designs are signed off. Your proposal gives a fixed plan.
Shopify migration
A replatform is the riskiest week in an online store’s life. Done carelessly, it costs search rankings, customer accounts and tracking all at once. Choose the platform you are leaving to see what moves, what tends to go wrong and how we handle it.
The most common move we make. WordPress plugins, hosting, security updates and checkout quirks are swapped for a hosted platform your team can run without a developer on call.
Usually a move away from high hosting and development costs. The work is mostly in untangling customisations built up over years, and deciding which ones the business still needs.
Data structures are similar, so catalogue migration is usually clean. The work is in themes, apps and making sure the new store converts better than the old one did, rather than just matching it.
Usually a growing brand that has outgrown its first platform. It is the moment to get the catalogue, tracking and product pages right, because they will carry the next stage of growth.
Crawl the old store, export Search Console data and list every product, page, app and integration.
Fields, variants and metafields mapped; product data cleaned rather than copied as-is.
Repeated imports into a development store until counts, prices and stock reconcile.
301 redirect map loaded, tracking verified, real test orders placed end to end.
Low-traffic launch window, then rankings, 404s, conversion and revenue watched daily.
What we build
Every app adds a monthly fee, more script weight and another thing to break. Where it makes sense, we build features into the theme instead, so the store stays fast and you own the code.
Build-your-own bundles and kits that raise order value without discounting the hero product.
Used on Supreme CBDA cart drawer with relevant add-ons and a free-delivery progress bar, built natively rather than bolted on.
Used on Steven Brown ArtTrade price lists, company accounts, payment terms and quick order forms on Shopify Plus.
Shopify PlusSubscribe-and-save, replenishment and member pricing, with self-serve customer portals.
Recurring revenueSell globally: local currencies, languages, duties and domains from one store.
InternationalPrivate apps and Shopify Functions for pricing, discount, delivery and checkout rules no app store app covers.
BespokeFilters by the attributes your customers actually shop by, predictive search and merchandised collections.
DiscoveryERP, EPOS, 3PL, PIM, Klaviyo and review platforms connected, so stock, orders and customer data stay in sync.
OperationsShopify in numbers
Shopify is still growing at around 30% a year on a very large base, and the UK is its biggest market outside the US. A crowded platform rewards stores that are faster, clearer and better built than the theme next door.
sold by merchants through Shopify in 2025, up about 29.5% year on year.
Shopify FY2025 · Feb 2026live Shopify stores in the UK, Shopify’s second-largest market after the US.
Store Leads · 2 Oct 2026higher conversion when shoppers use Shop Pay instead of guest checkout, in a study Shopify commissioned.
Shopify-commissioned study · 2023apps in the Shopify App Store. Useful, but each one adds weight, fees and risk.
Shopify Form 10-K · FY2025faster on mobile lifted retail conversions 8.4% and order value 9.2% across 37 brands.
Deloitte & Google · 2020updates in Shopify’s Spring ’26 Edition, centred on selling in AI channels and a redesigned checkout.
Shopify Editions · 2026Year-on-year growth in gross merchandise volume (GMV), by segment
of UK web traffic is on mobile (Statcounter, September 2026). Your product page is a phone screen first, which is why we design and speed-test mobile first.
Sources: Shopify FY2025 results via Digital Commerce 360 (17 Feb 2026); Shopify Q2 2026 results, SEC Form 8-K (5 Aug 2026; GMV $115.6bn, +32%); Shopify Q4 2025 earnings call (11 Feb 2026); Store Leads Shopify report (updated 2 Oct 2026; other trackers give different UK counts); Shopify Enterprise blog (18 May 2023, citing a Shopify-commissioned study by a consultancy); Shopify Form 10-K FY2025; Shopify Editions Spring ’26 (150+ updates); Statcounter, UK platform share (September 2026); Deloitte and Google, Milliseconds Make Millions (2020; data from late 2019).
Store health scorecard
Tick what your store already does. You will get a score out of 100 and the fixes we would prioritise, in order of likely impact on conversion rate and order value.
Indicative only. Points are weighted by where we typically see the largest effect on conversion rate and order value in Shopify store audits; your store’s numbers will differ. A free store review replaces this checklist with your own analytics, speed data and theme code.
Why Castle
Most Shopify projects stall after launch because the people who built the store are not the people trying to sell from it. At Castle they are the same team, which is how we focus on long-term success rather than launch day.
| Feature | Castle | Freelance developer | Build-only agency |
|---|---|---|---|
| Shopify Partner team: strategy, design, development and QA in-house | Yes | No | Yes |
| Conversion and order-value targets agreed before the build | Yes | Rarely | Sometimes |
| Designs approved in Figma before any code | Yes | Sometimes | Yes |
| Migration with a full redirect map and SEO checks | Yes | Sometimes | Yes |
| Paid media, SEO and email in the same studio | Yes | No | No |
| Ongoing CRO and A/B testing after launch | Yes | No | Extra retainer |
| You own the theme code and the store | Yes | Yes | Not always |
| Support terms | 30-day rolling | Ad hoc | Often 12 months |
Comparison reflects how Castle works and common market practice; it is not a review of any named provider.
The team
Castle is an award-winning Shopify partner agency, and our Shopify designers and developers work in the same Liverpool studio as our paid media, SEO, email and creative teams. When a product page needs changing to support a campaign, it is a conversation across the room, not a ticket to a third party.
Further reading
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Because we are measured on what the store sells, not just on delivering it. Strategy, design, development, migration and ongoing optimisation sit with one in-house team in Liverpool, alongside the paid media, SEO and email specialists who drive traffic to it. Published results include a 37% conversion-rate increase when Geepas’s rebuilt store launched and 53.85% revenue growth in 2021 for Supreme CBD on Shopify Plus.
It depends on the route. A customised premium theme is the most cost-effective; a bespoke theme costs more because it is designed and coded from scratch; Shopify Plus and headless builds are larger projects with integrations. We scope each project after a free store review and give you a fixed proposal, rather than a price range that changes later.
Typically 4–8 weeks for a customised theme, 10–16 weeks for a bespoke theme and 16–26 weeks for a Shopify Plus or headless build. The biggest variables are catalogue size, integrations, migration complexity and how quickly content and design sign-off happen.
Not usually at the start. Shopify Plus earns its fees when you need checkout customisation through Shopify Functions, B2B and wholesale on the same store, multiple expansion stores, higher API limits or Shopify Flow automation at scale. We will tell you honestly if standard Shopify does the job.
Yes, provided the migration is planned properly. We inventory every indexed URL from a crawl and Search Console, map each one to its new Shopify URL with 301 redirects, carry across titles, descriptions and content, verify structured data and tracking before launch, and monitor rankings and 404s daily for the first month.
WooCommerce, Magento and Adobe Commerce, BigCommerce, Wix, Squarespace, Etsy and custom-built stores. Products, variants, customers, order history, content and redirects move across. Customer passwords cannot be migrated on any platform, so we plan a reactivation email sequence.
A premium theme, customised well, suits many stores and gets you live faster. A bespoke theme makes sense when your brand, catalogue or buying journey does not fit a template, or when conversion rate and order value are the main constraint. Supreme CBD and Steven Brown Art both run on bespoke Castle themes.
Yes. Many clients come to us with a store that works but under-converts. We audit analytics, speed, product pages, cart and checkout, then run a prioritised programme of fixes and A/B tests. The scorecard on this page shows the kind of fundamentals we check first.
Yes. The Shopify store, its data and the theme code we build are yours. We work in your Shopify account with collaborator access, and keep code in version control so it can be handed over or maintained by another team if you ever choose to.
Yes. We offer retained development and support on 30-day rolling terms: bug fixes, theme and app updates, new features and landing pages, and a quarterly roadmap. Most Shopify clients also keep us on for CRO, paid media or email, because the store keeps improving after launch.
Free Shopify store review
Send us your store URL. We will review speed, product pages, cart, checkout, apps and tracking, and come back with the fixes we would make first and whether a rebuild is worth it.
