Hi British Guy,
Have a friend who converted his FAA license to Malaysian license. He did all the basic papers (CA6, Performance, HPL, all Malaysian DCA papers), had to do some single engine flying (approx 50 hrs), took the check ride for CPL, did twin engine flying for his multi engine rating, and did his IR check. It took him about a year to get Malaysian CPL/IR. Luck was on his side (and he's also a local), today he is a B737 commander in MAS.
I'm sure you can do it but I think you will have to go through the whole thing that my friend went through...