Thank you BMW
Mcs in garage with few probs. had phone call! Build up of carbon. Warranty doesn't cover de coking ( think that's the correct term). Cost ) £1300 . Keep the car I said because I haven't got that kind money. Phoned BMW head office told them the problem and the fact they said my daughter doesn't give it a good run that's why it's build up. She does give it a good run out and has put 10000 miles on it in 9 months. Anyway as a good will gesture BMW are covering cost. I am one relieved mother.