I bought an 56 Audi A3 1.9TDi with 80,000 miles last week from a reputable dealer. On the test drive we commented that it sounds like a police car siren. There was a noise coming from the turbo which the salesman said was normal. We were unsure and worried, but were told it'll be checked out. On picking it up we were told they'd done their checks and taken it to Audi, and there was nothing wrong. It's just a high mileage car and is normal, plus you've got three months' warranty so you'll be fine.

A week later it's driving us potty. We've had two independent inspections (one at a Volkswagen/Audi specialists) and a third over the phone, and one by a turbo repair specialist. All confirm the turbo is faulty. We took it back to the dealer who says they had it checked and there's nothing wrong. They said that they are "not going to replace everything that's old on a secondhand car". They have said they will take it to Audi next week for another check but I just don't trust them. Any advice on where we stand regarding warranty cover and legal advice?