If you have a ICAO CPL/IR, you can only convert it to a JAA CPL/IR which means doing the 15 hours IR training and the CPL as required training.
You can only convert like for like, belive me i tried, i had all the requirements for a JAA ATPL ,but i had a FAA CPL/IR, and they were 100% that i couldnt do a Mulit Pilot Type Rating and be issued with a ATPL. I had to upgrade mine to the ATPL first and then convert over. I kept asking why i couldnt do the JAA ATPL skills test and all they kept saying is it has to be like for like, unless you had a ATPL and then you could do the CPL/IR route if you wanted.
One other thing to be aware of is, as i had a FAA CPL i wanted to do the FAA ATPL checkride one day and the next do the JAA one, but they wont allow that either, as the FAA issue you a temp 120 Certificate, you have to wait for the permanant one to come through, i am not sure which License you have, but just be aware of that too.