I'm in the same situation, was working on my FAA Cpl ME IR so that when I got back to the UK I could complete the JAA ground exams, then demonstrate flying capability, then take the Cpl IR JAA practical exam. No such luck anymore, they require a full IR Cpl training course regardless of current hours or licenses. I was told that with MCC/CRP this amounts to the tidy sum of 23000 british pounds.
I am starting the ground school hopefully in April.
Just my luck, spend a ton of cash in the US, then have to retrain in the UK all over again!