Wibbly P, This question will be asked time and time again! if it's that boring don't read the post. If people who have FAA licences want to then get a JAA one, the best place to find out is PPRUNE. Why not help them out, instead of putting them off.
I think Redsnail is wrong about needing a class 1 to take the exams. You don't even need a JAA PPL to take the ATPL theory exams. You can do them with a foreign licence.