The IMC rating was designed to allow pilots to fly IFR outside controlled airspace in their own aircraft using whatever equipment it had fitted hence there is no specific requirement to do particular approaches other than one must be pilot interpreted.
Initially there were only a few civil airfields notified in Schedule 8 that you could make approaches to but that was scrapped in 1996.
There is nothing to prevent GPS approaches being conducted as part of an IMC course, if you have the appropriate equipment and can find one.
2/3 of the course is basic IF, the remainder is being able to fly two different approaches using whatever is fitted to the aircraft. It must however cover the basic IF and limited panel and the candidate should be able to use anything fitted to the aircraft so that leaves only a small proportion of the time to cover the GPS element.
There was a committee looking at revising the syllabus to include the GPS a couple of years ago but changes were inappropriate if the rating is to cease.
EASA have said that pilots holding IMC privileges will be afforded grandfather rights until alternative arrangements are put into place. The crackpot En-route IR appears to be the first step!
EASA Flight Standards: Instrument Flying