Peter Panpan,
I am in a similar situation. I have an FAA ATP (H), FAA issued S-61 and S76 Type ratings, and a UK issued JAR CPL. I want to convert my IR, and of course I must show a ME rating for the IR. I asked the CAA, and 3 weeks later I got my reply. I must complete a ME type in JAR land along with my IR conversion. No credit toward my previous multi engine time given. It doesn't matter I have 3000 hours in Med and heavy Multi-engine helicopters, I still must pay for an extra 5 hours in a twin squirrel to get the ME rating.
I have decided to stay with my current job (overseas flying on my FAA license) for now instead of going this route. Good Luck to you.