There was a discussion about this a couple of weeks ago. Might be worth having a trawl. I think the gist was, it is possible. I think you have to do something like, do the CPL but hold off actually sending away the forms for the licence until after the IR, then apply for both at the same time and the IR momentarily gets attached to your PPL before then getting attached to your CPL. I think then that means that you get credit for the IMC. But I'm probably wrong.
TB