Yes it is a seperate national rating. Intially they did give it and said that a MPA IR kept it current.
Then an ATPL MPA IR crashed on partial panel so they had a rethink and said you had to do the test. Can't really get worked up about that to be honest.
If you have a look through lasors at the IRI qualification
Basically its anything which leads to an instrument rating. The pre JAR FI rating made you get this restriction removed before you became unrestricted and JAR you didn't. EASA have a seperate rating the IRI which is going to cause problems with keeping people valid.
It has always been that any FI could teach the 180 to escape cloud instrument flying for PPL/NPPL.
There was a method under JAR that you could keep a SPA SEP IR valid through experence hooked on the back of your MPA IR. Only ever met one pilot that managed that and don't have a clue if you can do it under EASA.
Sounds like you have a JAR license which means no imbeded rights of the IMC.