Custom Software vs Odoo for an SME in London in 2026

The verdict in three sentences

Odoo wins when your process can adapt to the standard: fast rollout, controlled entry cost, a rich module ecosystem. Custom software wins when your competitive edge IS the process: atypical business logic, deep integrations, zero functional compromise. Over 5 years and 30 users the total cost gap is smaller than most expect (often under 20 %): the real question is business fit, not the sticker price.

The 2026 cost comparison

The two models have different cost shapes. Odoo bills a per-user monthly licence plus a one-off integration; custom concentrates cost in the initial build, then an annual maintenance fee. 2026 orders of magnitude for a London SME with 30 users.

5-year TCO for 30 users

Total cost of ownership (TCO) settles the debate more honestly than the initial quote. 2026 assumptions: Odoo Enterprise at 35 EUR/user/month, median integration 35,000 EUR; custom at 80,000 EUR build and 12 % maintenance/year. Hosting estimated separately.

The gap sits within a 15-20 % band. Beyond that number, what should decide: how many of your processes get bent to fit Odoo, and how many hours that costs each month.

Decision grid

Choose Odoo if: your processes are close to standard (classic purchasing, sales, stock, accounting), you want to ship fast, your team accepts aligning to the tool, and you value a ready-made module ecosystem. Choose custom if: your business has unique logic (atypical pricing, regulated workflow, specific production chain), you have heavy integrations with existing systems, you refuse dependence on a vendor's roadmap, or you want a product that becomes a resellable asset.

Mini case study

Thomas runs a building-materials trading SME in London, 30 users, margins computed on complex client price schedules. Odoo quote: 35,000 EUR integration + 63,000 EUR licences over 5 years = 98,000 EUR, but the specific margin calc needs a fragile overlay estimated at an extra 18,000 EUR plus 6 hours/month of manual workaround. Custom quote: 82,000 EUR build + 49,200 EUR maintenance = 131,200 EUR, process covered 100 %, zero workaround. Factoring the lost 6 hours/month (at ~45 EUR/h, ~16,000 EUR over 5 years) on the Odoo side, the real gap drops below 15,000 EUR. Thomas picks custom: margin protected, asset owned.

FAQ

Is Odoo really cheaper long term? Not always. Per-user licensing compounds: at 30 users over 5 years it exceeds 60,000 EUR, pulling the two TCOs close together. Below 10 users Odoo keeps a clear edge.

Can you customise Odoo without breaking it? Yes via modules, but every overlay complicates version upgrades. Beyond 3-4 heavy custom developments, custom software is often more stable and cheaper to maintain.

How long to go live? Roughly 3-6 months for Odoo, 5-8 months for custom in 2026. Custom can ship a working MVP in 3 months if the scope is cut well.

Who owns the code in custom builds? You do, if the contract assigns the rights. It is an asset: full reversibility, no vendor dependence, and it can be sold with the company.

What about AI? Both models embed AI building blocks in 2026 (document extraction, forecasting). Custom allows sharper targeting on your data; Odoo offers standard modules that deploy faster.

Let's scope your project. Tell us your user count, your 3 most critical processes and an indicative budget: we price the Odoo scenario AND the custom scenario side by side. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.