Hi GKD,
It is best to avoid the problems in the first place and I have written a useful guide to
buying a second hand car for this purpose.
You have the same rights when buying a second hand car that you have when buying anything. However, with a second hand car it really depends whether the problems are reasonable for a car of its age, mileage and price. It also depends what the seller said about the vehicle and when the faults appeared.
I'll write a new detailed guide when I get a chance
Tony