I had the same problem recently when the CAA came out with this BS that if you hold a JAA PPL then you must hold a JAA FI to teach CAA students overseas.
The scenario we had was yank CFI's that had never seen the CAA PPL syllabus and yet they were 'allowed' to teach the JAA PPL. Then we had the Brit CFI's that held a JAA PPL and know the syllabus as we was taught it and then the CAA tell us we can't teach it. Typical CAA, what a load of old bo**cks.
It got to the point where one of the Brit CFI's with a JAA PPL phoned Gatwick and requested that his license to be revoked and removed from the records. That way we could continue teaching overseas and complied with these ludicrous CAA rules. To cut a long story short, we never handed back our JAA PPL's to the CAA and was authorized to continue teaching. Since then I have trained 6 JAA PPL's whilst holding a JAA PPL myself/FAA CFI.