Heated rear seats are now fitted. The BMW garage arranged for someone to come in and install them. He was supposed to fit the BMW factory fit buttons under the four zone air con unit, but the fitter gave some excuse why he couldn't and fitted his own buttons either side of the 12v sockets. I think it was easier for him and the dealership just fell for his excuse and said ok. A bit disappointed but at least I have heated seats and a dealership warranty.