I don't think you stand much chance of seeing any money mate. If i was you i would squirt brake fluid on the bits that you painted (if you can do it without getting caught), if he comes back to you to ask you to repaint them i would add the cost of the first job onto the cost of the repaint but demand the money from him in advance. If he goes elsewhere for the repaint at least you have that satisfaction of knowing he's gonna have to part with some cash and more than likely a lot more than if he'd just paid you what he owed you.