Realistically, going to court is probably not worth the candle. I took a client a few steps along that route once; ended up losing a packet in actual money, the client as well as his ad. agency, and realising that the client's house-lawyers were better than the high street guy I'd gone to see, I had to back off and cut my losses.
For me, it was lack of legal knowledge: I hadn't reaised the difference between a principal contractor and his client... in short - I was abroad doing a shoot, the ad. agency had negotiated a week's work with me, but their client's foreign manager was at the shoot, and he asked and authorized that I remain working a second week, after checking back with HQ in Scotland. When I billed the agency for two weeks, they refused to pay more than the one week, saying I hadn't negotiated the extension with them, so I went after the client who had authorized the extra week, which I'd imagined he'd cleared with the ad. agency... young sucker comes to mind.
And then some people here have the nerve to look upon me as cynical! Me! With my smooth path through photographic life!
Rob C