With my financial assistance my grandson bought a 2003 Vauxhall Bora, 1.9 TDI, 113,00 miles, with warranty from a local dealer. It cost slightly under £3000 on 10 June 2013. My grandson is 18 and has been driving his mother's car for a year without any incidents.

Within a week the Bora had a major engine disaster. I do not know about engines, but understand it was a broken piston that went through the engine, doing lots of damage including to turbo, fuel pump etc., etc. This happened when he was pulling from traffic lights on outskirts of Norwich in traffic. The dealer immediately sent out a breakdown truck to collect the car and took it to a small garage he uses regularly. Since then my grandson has been told they have sourced a replacement engine from a Polo with less mileage and the car will be "ready tomorrow". This has been going on for five weeks.

I have now become involved and told the dealer we would like our money back and are willing to contact Trading Standards. The dealer is refusing to refund us. He has now told me that the warranty insurer has refused to pay any costs because its inspector has said the damage was caused by driver error, specifically because this damage has never been known on this particular engine, and the driver must have gone from "high revs in fifth gear down to first". The dealer says he is having to meet the substantial costs of repairs, etc. out of his own pocket and thus he cannot refund the cost of the car to us. I have totally lost confidence in this car and the dealer. Please what are our rights and is it worth fighting?