The verdict in three sentences
A reliable ERP connector costs between £8,000 and £22,000 in London in 2026, depending on whether you plug into a clean REST API or a locked-down legacy ERP. The most underestimated line item isn't development but error handling and synchronisation — that's where 70 % of rushed projects fail. Return on investment comes from eliminating double data entry and real-time data, not from elegant code.
Which integration modes, and at what budget?
Not every ERP integrates the same way. A recent Odoo exposes a documented REST/XML-RPC API; an old Sage or a locked SAP ECC forces a middleware or a nightly ETL export. Here are 2026 ballpark figures for the London market.
| Integration mode | Typical case | Connector cost (£) | Timeline |
|---|---|---|---|
| Direct REST API | Odoo 17, modern cloud ERP | 8,000 - 12,000 | 3-5 weeks |
| Webhooks + API | Real-time event sync | 10,000 - 15,000 | 4-6 weeks |
| Middleware (iPaaS) | SAP, Sage, multi-system | 14,000 - 22,000 | 6-10 weeks |
| Nightly ETL batch | Legacy ERP without API | 6,000 - 10,000 | 3-5 weeks |
| Bidirectional connector | Write AND read to ERP | 16,000 - 22,000 | 8-12 weeks |
Bidirectional (the app writes into the ERP) is always pricier: you must handle conflicts, locks and idempotency so you never create the same order twice.
The traps that blow up the invoice
Cost overruns almost never come from the happy path. They come from edge cases nobody anticipates at quote time. Budget them upfront.
| Technical trap | Consequence if ignored | Fix cost |
|---|---|---|
| Rate limits | App blocked at peak hours | £1,800 - £3,500 |
| No idempotency | Duplicate orders/invoices | £2,600 - £5,200 |
| No retry queue | Data lost if ERP goes down | £2,200 - £4,400 |
| Incomplete field mapping | Inconsistent production data | £1,300 - £3,500 |
| No monitoring | Silent failures undetected | £1,800 - £3,000 |
A serious connector includes a retry queue, searchable logs and alerts: if the ERP is unavailable for 20 minutes, no data is lost — everything replays automatically.
Mini case study
Sarah, finance director of a 45-person manufacturing SME in Croydon, manually keyed every B2B website order into her Sage ERP. Two people spent 6 hours a week on it, with a 3 % entry-error rate. The bidirectional API connector cost £16,000. Direct saving: 12 hours/week at £26 loaded cost, roughly £16,200 a year — the integration pays for itself in 12 months, before even counting the end of stock errors and the 2 days saved on monthly close.
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FAQ
How long does ERP integration take?
Expect 3 to 5 weeks for a modern REST API, 6 to 10 weeks for a middleware on SAP or Sage. Timeline depends mostly on the quality of your ERP's API documentation and your vendor's availability.
REST API or middleware: which to choose?
If your ERP has a clean REST API, connect it directly (£8,000-£12,000). A middleware (iPaaS) is justified beyond 3 systems to sync or on a legacy ERP with no usable API.
What happens if the ERP goes down?
With a retry queue, nothing is lost: operations are queued and replayed automatically when the ERP returns. Without it, every outage means lost data and manual re-entry.
Do I pay a recurring subscription?
A custom connector has no licence, only hosting (£25-£70/month) and maintenance. An iPaaS like Zapier/Make bills by volume, which gets expensive beyond a few thousand operations/month.
Can we sync in real time?
Yes, via webhooks: each event (new order, stock change) triggers sync within seconds. Nightly batch stays cheaper but tolerates a 24-hour lag.
Let's scope your project. Tell us your ERP (vendor, version, available API) and the flows to sync (orders, stock, invoices) and we'll price the right connector. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
