Most online stores start on a SaaS platform, and for a lot of businesses that’s the right call. Shopify, BigCommerce, EKM and the rest get you trading in weeks. The trouble usually starts later, once orders, channels and integrations have grown past what the platform was built to handle, and the workarounds start costing more than the convenience is worth.
ByteGears builds bespoke e-commerce platforms for UK businesses that have hit those limits. We’re a London-based development consultancy, and we know the UK side of this well: VAT and Making Tax Digital, the Consumer Contracts Regulations, the PCI scope decisions that keep card data off your servers.
We won’t tell you to leave SaaS if SaaS is genuinely working. If your catalogue is standard, you sell on one channel and you’re under roughly £5M turnover, a hosted platform is probably the sensible answer and we’ll say so. This page is for the businesses past that point, the ones where the platform has become the bottleneck rather than the launchpad.
Where off-the-shelf e-commerce platforms fall short
SaaS platforms are excellent at getting a standard store live quickly. The problems tend to show up as the business gets more complicated:
- Rigid workflows. Unusual pricing, commission structures and approval chains often can’t be expressed in the platform, so your team adapts to the tool instead.
- Costs that scale with you, not your margin. Transaction fees of roughly 0.6-2.9% per order, per-staff-account charges as the team grows, and paid apps at a few pounds a month each. None of it large on its own; together it’s a budgeting headache.
- Integrations that are really one-way syncs. Accounting, ERP, PIM and CRM connections often run as nightly batch jobs or bolt-on apps, which leaves inventory stale and creates data silos rather than one joined-up system.
- Multi-channel data going out of sync. Selling on your own site plus Amazon and eBay routinely leads to overselling: stock shows available on one channel after it’s exhausted on another.
- Platform limits on growth. Variant caps, inflexible shipping rules, weak B2B features and headless options gated behind expensive tiers all become real constraints at scale.
- Compliance that feels bolted on. Generic GDPR and VAT support is fine for ordinary cases but rarely covers industry-specific audit trails or data retention rules, and your finance team is left unsure it will pass an HMRC audit.
- Lock-in. Your customer list, order history and business intelligence sit inside the vendor’s system. If terms or prices change, the cost of leaving rises with every order you take.
The end state is a pile of CSV exports, Zapier workarounds and reconciliation spreadsheets, plus a quiet worry that a webhook missed an order during last weekend’s sale.
What ByteGears builds instead
A bespoke platform isn’t about rebuilding Shopify with your logo on it. It’s about the parts of your operation that a generic tool can’t model well.
It fits how you actually trade
We map your real workflows first, then build software around them, the proprietary pricing, the commission splits, the approval chains. If those rules are part of what makes you competitive, they belong inside the system rather than in a spreadsheet beside it.
One set of data across every channel
Your own site, marketplace listings, POS and B2B portal share the same inventory, order and finance records. No nightly sync, no overselling, no aggregating orders by hand on a Monday morning.
Integrations built in, not bolted on
Direct connections to your ERP, accounting software, PIM, CRM and logistics tools, designed as part of the system. Where third-party APIs are flaky, we add queuing and polling fallbacks so a failed webhook doesn’t quietly lose an order or a payment.
UK requirements handled properly
VAT across jurisdictions and rates with MTD-compatible exports, GDPR consent and data-subject controls, PECR cookie consent, and the 14-day cooling-off rules under the Consumer Contracts Regulations. For regulated sectors we can embed the specific audit trail and retention rules your compliance team needs to sign off.
You own it
One build cost and the code, data and roadmap are yours. No per-seat fees as the team grows, no transaction cut, and no migration ransom if you ever want to move hosting.
Architecture that can grow
Modular by design and headless-capable, so you can add subscriptions, a B2B portal, a native mobile app or another marketplace later without starting over.
Features we typically build
Every build is scoped to the business, but most include some version of these:
- A responsive, fast storefront, with mobile treated as the primary experience rather than an afterthought
- Product and catalogue management for variants, SKUs, bundles, digital downloads and services, with bulk import and export
- Real-time inventory across locations: quantity on hand, reserved against orders, available to sell, with low-stock alerts
- A checkout you control: guest checkout, saved carts, abandoned-cart recovery and multiple payment options including digital wallets and BNPL
- Order management in one place, covering capture, status tracking, customer communication, returns and RMAs, and partial shipments
- Customer accounts with order history, saved addresses, wish lists and loyalty tracking, plus B2B company accounts with multiple users and roles
- Tax handling that calculates VAT by location and class and logs every transaction for HMRC
- Marketplace and channel sync for Amazon and eBay, with careful SKU mapping so the right product ships
- Reporting on revenue, average order value, conversion, repeat-customer rate, slow movers and stock turnover
- Staff permissions granular enough to match how your departments actually work
B2B-specific work, tiered and customer-segment pricing, purchase orders, credit accounts, requisition lists and quote management, is common and usually phased in once the core platform is stable.
How the work goes
Discovery and planning (2 to 3 weeks)
Workshops to document your processes, pain points and technical requirements, plus a look at your existing systems and data. This phase decides what migrates, in what order, and what “done” means. Skimping here is the most common reason e-commerce projects overrun.
Build (8 to 16 weeks)
We start with a working MVP, catalogue, checkout, one payment gateway plus a backup, order management, inventory sync, customer accounts and the security and GDPR basics, then add channels and integrations in phases. Regular reviews mean you can course-correct as the platform takes shape.
Migration and testing (2 to 4 weeks)
Product, order and customer data migration with an early data-quality audit, since duplicate SKUs and missing images are the norm. We favour a phased cutover with old and new running in parallel over a single big-bang switch, plus full testing of checkout, tax and payment paths before anything goes live.
Launch and support (ongoing)
Role-specific staff training and documentation, hands-on cover through the first 48 to 72 hours when real-world issues surface, then an optional maintenance package for updates, security and new features on your timeline.
What it costs
A bespoke build costs more up front than a monthly subscription. As a rough guide, a focused MVP sits in the low tens of thousands; a mid-market multi-channel platform with integrations and custom workflows runs higher; an enterprise build with headless storefronts, a B2B portal and ERP integration is a larger commitment again.
The honest comparison is five-year total cost of ownership, not month one. Against custom you should weigh:
- Subscription tiers plus transaction fees on every order
- Per-staff-account charges that climb as the team grows
- Paid apps and middleware that accumulate quietly
- The labour cost of manual exports, reconciliation and overselling fixes
For lower-volume single-channel stores, SaaS usually still wins on those numbers and we’ll tell you so. For higher-volume or multi-channel operations, the maths often tips the other way, and you also stop paying to differentiate yourself. We model your actual figures in the consultation rather than promise a fixed payback date.
Who this works for
We’ve built or scoped this kind of platform across a range of UK sectors, each with workflows a generic platform handles awkwardly:
- Fashion and apparel: heavy variant management across size, colour and material, trend-driven inventory, social selling and return-and-exchange workflows
- B2B wholesale: tiered pricing by volume and customer segment, company hierarchies, purchase orders, NET-30/60 credit terms and account-specific catalogues
- Food and drink: subscription and meal-kit billing, expiry-date tracking, HACCP logging, refrigerated shipping and local delivery zones
- Furniture and home: large product imagery and 3D models, configure-to-order products, and shipping logic for heavy items and white-glove delivery
- Health and beauty: ingredient filters, subscribe-and-save options, prescription validation and appointment booking
- Digital products: instant delivery of files and licences, subscription access for courses and software, no shipping logic
- Subscription boxes: recurring billing with pause and resume, and inventory planning around monthly variations
- Marketplaces: multi-vendor management, commission tracking, payouts, seller ratings and dispute resolution
- Membership organisations and charities: renewals, members-only content, donations and Gift Aid processing
If you’re not sure which side of the build-versus-buy line you fall on, that’s exactly what the consultation is for. We’d rather point you at the right SaaS plan than sell you a build you don’t need.
Common Questions About Custom E-Commerce Platforms
Do we actually need a custom platform, or is Shopify fine?
For a standard catalogue, single-channel selling and turnover under roughly £5M, a SaaS platform like Shopify, BigCommerce or EKM is usually the sensible choice and we'll tell you so. Custom only pays off when SaaS constraints are genuinely holding you back: proprietary pricing or commission logic, multi-channel selling that has to share one set of inventory and finance data, deep ERP or PIM integration, or per-seat and transaction fees that have grown faster than your margin.
How does the cost compare to staying on SaaS?
A bespoke build costs more up front than a monthly subscription. The honest comparison is five-year total cost of ownership: subscription tiers, transaction fees of roughly 0.6-2.9% per order, per-staff-account charges, paid apps, and the labour spent on CSV exports and manual reconciliation. For higher-volume merchants those numbers add up quickly. We'll model your actual figures before recommending anything, rather than assume custom always wins.
What's a realistic timeline?
A focused MVP, working catalogue, checkout, one payment gateway, order management and inventory sync, typically takes 8 to 12 weeks. Multi-channel selling, accounting integration, B2B portals and headless storefronts are added in later phases. Larger builds with ERP integration run 4 to 6 months. We launch core functionality first rather than holding everything back for one big release.
Can you integrate with our existing systems?
Yes. Common ones include Stripe, PayPal, Worldpay and BNPL providers like Klarna and Clearpay for payments; Xero, QuickBooks and Sage for accounting; Royal Mail, DHL and 3PLs for fulfilment; and Amazon and eBay for marketplace selling. Where APIs are unreliable we build queuing and polling fallbacks so orders and payments aren't lost silently.
What about migrating our existing store and order history?
We treat migration as its own piece of work, not an afterthought, because most poorly planned migrations overrun. We audit data quality early (duplicate SKUs, missing images, orphaned orders are common), map products and variants carefully, and prefer a phased cutover with old and new running in parallel over a risky big-bang switch. Customer passwords can't be migrated, so a reset flow is planned in.
What about data security and compliance?
Builds include UK GDPR controls (consent management, data export and deletion, audit logging), VAT handling with MTD-compatible exports, and cookie consent under PECR. For payments we use hosted payment pages or iframe integrations so card data never touches your servers, which keeps you in PCI DSS SAQ A scope. UK-based hosting is available where data residency matters.
Do you provide training for our team?
Yes. We run role-specific sessions for admin and merchandising staff, finance, customer support and marketing, with documentation for each, plus hands-on support through the first 48 to 72 hours after go-live when most real-world issues surface.