It sounds very much like an manifested problem with the head unit given the mirrors are set up from it.
Is the dealer taking the pee saying they can’t do it untill May. I’d be straight on the phone to Motability in the morning expaining the car is now a danger to drive, as the mirrors are folding in when driving and the dealer can’t fit it in till May at the earliest. Let them sort it and put you in a suitable hire car and not a mini moke 🙂