As the vehicle has broken down so often and they have been unable to fix it, you are entitled to reject it. You should not have to pay £15,000 for anything; the seller is in breach of contract to a material degree. The vehicle is unsatisfactory. Give them 7 days to uplift the vehicle and refund your money. If they refuse, see you solicitor with a view to raising court proceedings. You have been more than patient. 47 breakdowns and 6 months in the garage is farcical. You should have no difficulty in succeeding with a case. I hope that helps. Please leave a positive rating so that I am credited for my time.