Finally - after about five months with a symphony of warning beeps when starting the engine - the car is fixed.
Back in January my ESP light came on randomly while driving, took it to a local place who said it was a faulty ESP sensor which would be £950 to replace.
Got one off eBay and fitted it myself but that didn't fix it so took it up to MRC - they did some further tests and updated the software on the ABS module which helped narrow the issue down and it looked like a fault with the ABS module, so that came out and went off to ECU Testing. They bench tested it and said it checked out so back to MRC for more investigation.
Had to take the car back due to lockdown and during that time I was getting 40+ faults on a scan, stuff like component protection active on seats, communication with other modules dropping off and other weird stuff, which maybe pointed to a battery/voltage fault. Got the car back up to MRC last week and the battery was fine but alternator wasn't charging high enough. Replaced the alternator, most of the faults cleared, but the ESP sensor flagged again so seat out, no issues with the sensors, but they found some corrosion in the plug itself so that had to be cut and repinned.
After that there was still a residual issue with the ABS - bad signal to the module and also not communicating properly with the rear left sensor. Wiring testing found a poor connection to the module for the rear left sensor, and then finally, in the loom that runs behind the wheel arch:
That was fixed, road tested, and finally it was done.
Got a couple of service things done too while it was in - rear pads and discs changed, and the thermostat was knackered so that got replaced too.
They think the ESP sensor under the seat must have got wet at some point, e.g. if something was spilled down there. The broken wire in the door is a bit more of a mystery, I had a repair done in there back in October so whether it got pinched when they were doing the repair and that allowed it to corrode, or it just something random, who knows.
As expensive as that was, I'm still delighted to have the car back and working. Had been thinking about selling it and getting a TTS but not sure this is really the best time to be buying a car, and I'd have taken a bit hit trying to sell it with those faults anyway.
Jobs for this weekend - give the glass a machine polish. The side windows are marked from going up and down, and the windscreen is a nightmare to see out of at night - wondered why this was the case but apparently years of scratches and swirls make the light refract differently so going to tackle that.