I bought an Audi A4 from an Audi dealer two years ago. It's been serviced by them since purchase, with the last service in December 2017. It recently broke down and had to be towed to the Audi garage. They're asking for £1500 just to take lid off the engine and look inside for some sort of compression problem. The car is worth about £7000 and they can't give me an idea of the final repair cost. I don't think it's worth paying for what looks to be a never-ending bill. Can I resort to litigation?