Dear Moggie,
There is no direct conversion from FAA to JAA licence unless that person has more than 1500 MCC time.
To convert his FAA CPL-IR to JAA CPL-IR, he will have to pass either CPL or ATPL exams. He will also be required to take a CPL and IR course. I am under the old system and even under the old system I was required to pass all the written exams. The only benefits I get is that I dont have to take the full CPL or IR course as long as I finish everything before June next year.
I hope this helps.