May as we'll do this now instead of waiting another week as I did an unexpected journey to Liverpool today - combined with the running around I've done since changing the brake switch it amounts to over 350 miles driving about and the fault has not reappeared at all.
Luckily for me the cheapest of the potential causes was the actual cause - the brake switch when dismantled clearly shows signs of electrical contact damage/wear and this was unquestionably causing the fault. Still stunned that a pinhead sized faulty component could knock so many systems out on such a modern, and small motor.
Happy ending folks. I like getting happy endings. Hopefully this thread will be of some use to peeps putting up with the same issue
where can i find the switch? are you able to take a picture of its location? thanks