Hang on a minute...
Bloke goes to buy a car. Puts down deposit on promise of work being done. Work gets done, and then the bloke calls up and says "oh sorry, I don't want the car anymore, can I have my deposit back?". Sorry, but why should the dealer have to suffer in any way, shape or form for this? Not only do you have his cost for the actual spraying that's come from another party (I assume), but you've also got his time for sorting it all out and then his time having the car in stock and not trying to sell it. That's a lot of wasted time and money, and he's not in the job to simply do people a favour.
If you put down a deposit on a car and then pull out, you should lose the whole lot. A deposit is there for the protection of both parties, and if one person puuls out why should the other suffer any kind of loss at all? Sure, as a gesture of goodwill he may want to give some back, but given you're unlikely to go back there to buy anything from him then I wouldn't blame him for keeping the lot. Sorry chaps, this is the real world where people have to make a living. He is fully entitled to keep the lot assuming the paperwork is correct, credit card or not, and if the paperwork isn't correct only then does it become the dealer's problem.