Strateandlevel
"Another point to note is that your multi-pilot IR will not be valid on single pilot aeroplanes however, if you have a UK ATPL you will effectively have IMC priviliges. A JAA ATPL does not include the IMC privileges."
I bet VERY few ATPLs know this. Incidentally, on the way to an ATPL you probably did a CPL/IR course of some sort which would have been a single-pilot IR, would it not? And if so, isn't this valid all the time your ATPL is valid? If not, is there an easy conversion?
I happen to know of some working ATPLs who self fly hire small planes and think they have full IR privileges. The answer to this would be very interesting.