A few weeks ago my husband's car broke down (2009 Ford Focus 1.6) and he called roadside recovery who diagnosed the head gasket had gone. We had it towed to the local dealership and told them what the AA had said. A few days later they contacted to say that it was not the head gasket and that it needed a new engine.

Obviously we were shocked as it had done 31,000 miles and is only a few years old. We paid them £500 for labour and had it towed to the dealership we bought it from (18 months prior) as directed by Ford to see how they could help us.
Now, two weeks later, we have been told it was just the head gasket, which has been fixed.

After complaining to the first dealership, all they have offered is money off our next service and they say they don't give compensation. What are our rights? Can we sue for their error?