How much does bespoke software cost? An honest answer for UK businesses

If you've reached this post, you've probably already worked out that you need something built. You've read the "should I build or buy?" articles, stared at your SaaS bill, and now you want a number before you email anyone.

So here it is: custom software for a UK SMB starts from around £2,000 for a simple custom site with a content management backend, and runs to £15,000–£30,000 or more for a system with multiple integrations, automated workflows, and business-specific logic. Projects involving full platform migrations with automated data pipelines sit at the higher end of that range and beyond.

What puts a project in one bracket or the other is worth understanding before you start any conversation.

The floor is a custom-built website or internal tool: five to twenty pages, a content management system so non-developers can update copy and images, a contact form, email handling. Something built on modern JavaScript, designed to be maintained and extended, not locked to a platform that forces a particular structure.

These start from around £2,000 and grow with scope. A 20-page site with a structured CMS, multiple content types, and a couple of integrations — a mailing list, a booking system — sits in the £5,000–£8,000 range. The complexity is low; the value is in having something that fits your workflow and that a developer can extend without starting from scratch.

Three things reliably move a project into a different bracket.

The first is multiple user types. A system where managers, staff, and external clients each see different data and can take different actions — what developers call Role-Based Access Control — is significantly more complex than a single-user tool. Each role adds a dimension of logic and testing that multiplies quickly.

The second is integrations. Connecting your software to external systems — supplier APIs, accounting platforms, existing databases, third-party services — costs proportional to how well-documented and reliable those systems are. One clean integration is manageable. Four integrations with inconsistent data formats, rate limits, and occasional outages is a different project.

The third is automation. Batch jobs, scheduled pipelines, anything that runs without a human pressing a button adds both engineering complexity and the ongoing cost of keeping it running when something upstream changes without warning.

The most complete project in our portfolio is a UK bike shop. They were running two completely separate systems: a point-of-sale platform managing in-store stock, and a WooCommerce site that was permanently out of date. Tens of thousands of products, most with missing descriptions, wrong titles, no tech specs, no images.

The work involved migrating both systems to a unified platform, then building a set of automated pipelines to fix the content problem. Brand adapters pulled tech specs and images directly from manufacturer APIs — Trek, Cannondale, and others. A rules engine identified products below a content quality threshold. An AI step rewrote descriptions for SEO. A separate pipeline pulled live stock availability from suppliers daily and published new products automatically. Email digests gave the shop owner oversight without requiring them to babysit the system.

Online sales went from roughly £2,000 a year to over £200,000 in year one.

That kind of project — platform migration, multiple external API integrations, automated content pipeline, AI augmentation, supplier feeds — sits well above the simple bracket. After launch, the ongoing work included building new brand adapters and tuning the AI prompts as the product range grew.

Every agency will tell you what the build costs. Fewer will tell you what happens after.

Software needs maintenance for the same reason a car does. Dependencies update, external APIs change their format, security patches come out, and small bugs that looked harmless on launch day compound over time. A project with three supplier integrations has three external systems that can change without warning.

We offer a monthly retainer for this reason — fixes, updates, and the next round of improvements. It's a working relationship with the developer who built the system and already knows how it works, not a support contract with a ticket queue.

Clients who skip the retainer and call when something breaks pay more per hour and wait longer. Urgent unplanned fixes cost more than maintenance that prevents them.

For a simple custom site with a CMS backend, expect to start from around £2,000. For a system with integrations, automation, and business-specific logic, £15,000–£30,000 is a realistic bracket — complex multi-integration projects sit above that.

Ongoing maintenance runs at a few hundred pounds a month for most projects.

If you want a number for your specific situation, a short scoping conversation is the quickest way to find out which bracket you're in.