the car is back and fixed.
symptomes were reduced voltage (3V) against the circuits indicated as faulty on the fusebox
garage tried an ecu swap and it made no difference, so they went back through the continuity loom check and they then found a short under the fusebox as it bends and passes through metal
(anyone got a picture of the loom routing under the fusebox by any chance?)
at that point they also worked out the relay had been taken out by the problem.
So in all
new relay
a few new fusebars (precaution)
new fusebox engine bay (changed but not convinced it was actually needed)
repair loom short
4 hrs labour
final bill was just short of £700, of which 50% is parts and 50% labour.
Garage have been brill in progressing this work, I left it with them indicating they had as much time as needed to resolve and no rush
that way they could work on it as and when around other jobs (they did way more than the 4hrs they charged for)
in hindsight Im not convinced on the fusebox replacement, but they also sourced a replacement unlocked ecu (temp) which i couldnt have done, nor was I charged for it.
moral of the story , its usually something simple.
Anyway the cars back and Ive missed it
thanks
@Pudding as ever for the interaction