I have recently bought a two year old Vauxhall Corsa from a major national dealer. The car had some technical difficulties - which the dealer was failing to repair - so I asked my local mechanic to examine the car. He has told me the car has had its engine changed. The dealer has since confirmed this and said it was fitted by the previous owner although the V5 makes no mention of the car having a new engine fitted.

My local mechanic believes the car has been involved in an accident, but the dealer is refusing to give me a refund as they say it's common for cars to be resprayed. They also say the fact that the engine isn't the original isn't grounds for a refund. What is the best thing to do in this situation?