Julian,
I binned the letter I'm afraid, but I got it in April. They basically said that I could file and fly IFR with an ICAO IR but NOT in controlled airspace. They included a section of the ANO which states the "NOT in controlled airspace"...thing....
{edit cause I've just found the relevant bit in the ANO}
ANO 2000, Part 4, Article 21, Paragraph 4 (a) says that the CAA will recognise a foreign rating / licence but (a)(ii) states:
"Does not entitle the holder to act as pilot of any aircraft flying in controlled airspace in circumstances requiring compliance with the Instrument Flight Rules or to give any instruction in flying"
I'll send it to you if I find it, if not, might be worth writing to them yourself, maybe they have changed their mind...
Cheers
EA