Electrical problem

[Niall]

It was an intermittent fault, which screams electrical fault to me, as a mechanical part will either be fine and work, or be f*cked and not work

Not necierally. Look at the old old fiestas. They had a problem with that. Problem is it was a box apart job to fix for a simple 30p part!

I would start with continuity checks on the wires. I will send you over some auto data drawings and you can check for broken wires.