I would suggest that you get the CAA PPL but it's too late!
It's pretty much of a muchness when it comes to flying in the UK, you can fly in the UK on an FAA licence and you can fly in the USA on a JAA licence (always provided that you get the necessary conversion). I think a lot of people who have spent a ridiculous amount of cash getting a PPL in the UK will have particular suspicions about US trained pilots so it is probably best on balance to get a JAA licence. Do be careful though, a some places in the states con you into believing that you will actually get a JAA PPL at the end of your training but then you only get a conversion which means that you end up with an FAA licence after all. This can lead to complications if you want to fly in France or Spain for instance.