Wrong again Grivation!
You can ONLY qualify for a JAR ATPL(A) by holding a multi-pilot type rating. The 'Commuter' types you specify are all classed as single-pilot aeroplanes under JAR-FCL and therefore wouldn't qualify you for the ATPL. However, as long as you have 500 hours multi-crew time in your commuter types AND you complete a TRTO course for a multi-pilot type (see Appendix 1 to JAR-FCL 1.220, Part B for the list of types) AND pass the ATPL Skill Test with a CAA Examiner, you WILL be credited the IR course. This, I believe, is the only way that you can avoid the requirement for an IR course.
The CAA detail this in their new LASORS document (page 304!).
Hope this helps
Flaps