do you know if you can cross-credit any previous dual instrument time towards the IR(H)?
Cheack Lasors & JAR-FCL 2. If memory serves me right the holder of a (JAR) IR(A) needs at least 10 hours of instrument training in a helicopter for the IR(H).
What about taking the Single Engine IR(H) and then a Multi-Engine IR(H) upgrade? This only requires 5hrs and a type-rating (which you would have to do anyway)
It shouldn't matter much if you go for the SE or ME IR(H). If you have your SE IR(H) it should be upgraded to ME when you do your type rating check-ride on a multi-engine helicopter.