Jerezflyer,
All basically correct. The course to convert from S/E IR to M/E IR is minimum 5 hours M/E IR training and another full IR test which is what puts most people off. Some people do the S/E IR as a way of 'banking' their exams if time is running out, but it doesnt really save any money in the long run and for most people one IR test is enough.
There are basically Single Pilot and Multi-pilot IR's which are then applied to the different classes and types of aircraft.
Bertie,
Sounds reasonable but as I say I couldn't comment on other JAA states rules.