Well I had a quick look at the earth cabling around the ECU and seems ok, but I don't have a decent multimeter to check the earth from there to the negative terminal on the battery. Must invest in one.
The car has not moved since the AA incident a couple of weeks back, but this morning the alarm went of randomly again, so I grabbed the old laptop and op-com, and plugged straight in to see if there were any new codes associated with the alarm. There were no new fault codes related to that (same codes as before). Whilst looking at the laptop, with ignition on, but engine not running at all, the traction control fault suddenly came up on the SiD, so I checked the codes and thought I got the same U2105 code I'd got before, but noticed it was actually U2103-00.
Not sure that makes much difference?
Got to get the car to Birmingham (if it'll make it) or find a local auto electrician who may be able to check the wiring/earths for me.