Hopeful Pilot,
I have completed my conversion from FAA - JAA groundschool in UK with BristolGS and the flights in Greece. All you need to obtain a UK JAR license is to complete a change of state application form, attach the fee to it (its no big amount check CAA website for an exact amount- just paperwork) and send it to the CAA.
If your looking for a school for the flight training portion let me know and i can get you a greate price with a school in Greece (the one i attended). Just as a basic guideline UK schools cost from 12000 - 17000 euros. In Greece you can get the same training for approx 7000 euros all in aircraft - no sim and change your Greek JAR license (Greece is JAR FCL 1 approved) to a UK or other with a change of state applications form to the CAA of your choice.
Hope this helps
Leon