I would be suprised if a JAA PPL was much cheaper in the USA.
I last flew in the USA in 2006 and already fuel there was way up on a few years before, and it has continued.
There is still a margin on the cost of self fly hire but it won't be the 3x margin which used to be say 10 years ago, which was great for hour builders who just wanted to stuff 1000hrs in their logbooks by flying up and down in a C150.
The real saving will be from the somewhat better weather in Florida compared to the UK, the continuous flying (as opposed to fitting lessons in between life's committments which is what people do here), and the better organised schools which keep their planes flying as much as they can.
My guess is a 25% saving on average.
If I was doing a JAA PPL in the USA I would use the school in southern California, where the weather will be much better than in Florida.
The saving on the FAA IR done in the USA versus the JAA IR done over here is massive - about a factor of 4. But that is for largely different reasons.