Hi BritishGuy,
A few schools in the USA have joined forces to bring a UK CAA JAR-FCL ATPL Written Examination Centre in Orlando, Florida.
If you're on a course with one of the schools then to use the examination centre is free (you still need to pay the CAA for the exams though) but if you aren't studying with one of the schools then they'll charge you $350 to use the exam centre.
The examinations are sat on the first Monday of every month. The timetable lasts for 4 days which covers all 14 subjects. I believe the timetable is the same as that would be at home in the UK.
Best wishes,
Charlie Zulu.