Well I traced the wires back to BSM fuse box under the bonnet, everything seemed to check out OK. Picked up the voltage at the multiplug from there where it goes up to the wiper motor.
So I've fitted a new BCM and all is Ok now.
Interestingly the engine seems to run more smoothly as well now. Customer has had random misfire codes logged occasionally. This unit also supplies the feed to the coil and injectors, so only time will show me if it was affecting this as well.