Mmmm, if it was owned by one of the owners, they are on dodgy ground mate imho. This is exactly what happened with my mate recently, fortunately he had finance and they are responsible, they will then pursue the dealer.
I would make a call to trading standards, get their advice, which i am sure will be in your favour and then if you are still not satisfied with what the garage says or does, let them know you have been in touch with trading standards, should do the trick
Think I will be contacting them today. I doubt he'll phone me back, they've had it for a week and not even been able to give me any information at all. A car should be sold that is 'fit for purpose' mine is not so I think I might look into a full refund. Seems like I could get a hell of a lot more car for my money...