There are 7 schools in USA approved to conduct training towards a JAR PPL (A), see page 5 of this document
http://www.caa.co.uk/docs/33/SRG_FCL_APPROVEDFTOS.PDF
I did my PPL in 4 weeks at Ormond beach recently, would have been 3 had Katrina and Rita descide not to pick the month I descided to go there. Hard work, but fun. I'd recommend doing the theory before going there.
If you are training now in the UK, you will indeed be training towards a UK JAR PPL(A). You'll have to ask the FAA with regards to using expericence gained in the UK for a FAA PPL. Like the UK, they may allow a small proportion.
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