A guy at my flight school is doing a single engine IR before his CPL and an MEP/muti-engine IR upgrade and he's finding it very tough.
I'm following the MEP->CPL->IR route, and my speed control has got so much more accurate during the CPL I'm doing now. I already have an IMC.
Only a brave man (or girlie) would attempt an JAA IR before his (her) CPL!
(forget the ATPL exams, coz they're bollox all use when it comes to flying an aircraft)