If you find the car "of unsatisfactory quality" due to a fault that has existed since delivery that has not been fixed despite more than three attempts, you can reject it under the ruling in Clegg v Olle Andersson (trading as Nordic Marine), House of Lords, 2003. See: www.honestjohn.co.uk/faq/consumer-rights/ However, at best, after having driven the car for 15 months (minus a month or so while in for repair), at best you can only expect a refund of current market value and, if the dealer chooses to fight your rejection, a County Court case will be very expensive with no guarantee of a ruling in your favour, nor of being awarded all of your costs.