EOBD (or OBD II as it's known in North America, and introduced in 1996) is a standard for engine emission data only. This was agreed by motor manufacturers and other motoring organisations, where previously different manufacturers used different software, interfaces and fault codes. It came into legislation in the UK on 1st January 2001 for petrol engines, and 1st January 2004 for diesels, and uses one of a few standard protocols. An EOBD scantool cannot be used for any of the vehicle systems such as ABS, Airbag, Instruments, HVAC, etc, other than engine emission data. It also cannot be used for engine specific data. You need a more specific scantool to do what you want to do.

Thanks for the advice, all - very helpful.

I did manage to borrow a friend's Autel AL619 that said it was compatible. It was able to read the code - showed C1350 Recirculation Pump. Not something I think I can deal with so I'll take it to someone more capable shortly (who has the proper diagnostics too).

In the meantime, I've tried the fuses I can get to - have now realised that two of the MAXI fuses are also for the ABS system but I struggled to get access to them. I've since found some more tips for getting to the MAXI fuses on the C3 (citroenc3owners.com/tips-for-any-citroen-c3-f8/c3-...l), so will have another go.