"Then come back to the UK and wonder why it takes you another 15 hours to learn to talk correctly on the UK radio, navigate around tricky UK airspace, fly on instruments, use a VOR etc, oh and don't forget the JAA checkride/CAA costs"
That would be for an IR conversion course (After type rating), we are talking about PPL here, no need to come back to the UK and do anything since he would be holding a JAR PPL issued by the UK CAA. All the CAA fees are clearly listed. Again: why are you suggesting more flying and training? That doesn't make any sense.
Then sit down when all is done and wonder why all that hassle going to the USA, coming back, doing more flying, paying for more training etc. only saved you £300.
Since when going to the US would be a hassle? Just go for it! You will save on the flight hours (Right now 1 hour on the S300 with a JAA Instructor goes for 327usd), on the fact that it will take you less time to do your training because of the good weather, the aircraft availability (Around 25 ships), the overall efficiency and getting stuff done philosophy, the absence of landing fees, the stimulating environment... Do I need to carry on?
Of course I am being facetious, but seriously, beware, going to the USA isn't always the cheapest/best option. Do you research, and don't believe all those "GET YOUR PPL IN 3 WEEKS FOR $9,999" adverts.
There is only one place in the States where one can do a JAR PPL(H) and that is Bristow Academy. If you look it up you will see all the info clear and transparent. You may want to consider getting a FAA PPL which is also a great option but then you need a 100 hours in order to convert to JAR... Might as well get the JAR first, then get a validation with the FAA and get your FAA Instrument Rating so that you have a FAA stand alone certificate.
If you are really on a tight budget just get your FAA PPL.