IO540:
an IMCR will give you single crew IFR privileges in UK airspace Classes D,E,F,G whereas your multi crew JAA ATPL will give you no single crew IFR privileges whatsoever
Surely that's not right? The guy's on a "structured modular course". That presumably means he will be doing a CPL followed by a ME IR on a single-crew piston twin. Therefore his IR when he gets it will give him all the single crew IFR privileges you can get. He won't lose those until that rating lapses because he doesn't do his annual route sectors etc. That MIGHT be because he's only then flying multi-crew aircraft, but might be because he's flying nothing, or only singles. And in any case he won't get an ATPL until he has 1500 hours and a type rating on a multi-crew type. Until that point his flying is done on a CPL.
NS