It's a bugger that is! The only way forward is to drop your price, on reading your first post I was going to suggest £500 off, I think that's the kind of drop I would want on a car in this price bracket for Cat D. In a way you're lucky he's still interested. But you have to face the fact that you've been stiffed, already, through no fault of your own, and you've just got to get on with it.