Car repairs not working...Where do I satnd?

[Le Chat]

My Audi had a series of problems, which resulted in us taking it to the main Audi dealer. They repaired the car and charged �280. Two days later the exact problems returned...only worse. We now have to tow it to them 40 miles away and they have said that if the part they fixed last time was faulty then they would replace it free of charge. However, anything else they would charge at their normal rate. So basically, the car has not been fixed properly and yet they want to charge us again to fix it! If I went to a hairdresers for a perm and it fell out 2 days later, I would expect the hairdresser to do it again for free and so would the hairdresser! Is there anything legally I can quote to them in order for my car to be looked at again and fixed properly, without me having to pay for their inability to solve a problem the first time, which at the end of the day, is their job? I am quite happy to pay for extra work but the �280 I have already paid should be deducted surely?