Hey,
the company that you took your car to has a legal obligation to get your car running back to the condition as when you took it in, if not contact consumer affairs and department of fair trading and i am sure he will fix the problem quick smart and if he does not suing him will be your only option, also PM with the garages details and i will chat to my sister who used to work for consumer affairs and see what she says........
Steve
X GTi-R X (PHAT32)