Interesting! I was told by a Doctor at the Gatwick Medical Division of the CAA that if I got an FAA license [PPL(H)] I would be able to fly in UK in 'G' registered aircraft under the ICAO regulations and would not officially need any other requirements. Flight schools may wish to impose Airlaw tests on you, etc but that would be htier requirement and not the CAA's.
I now have an FAA PPL(H), an FAA Class 3 medical with a SODA (Statement of Demonstrated Ability) which effectively means that my disability which prevents me from obtaining a straight forward medical is discounted because the FAA have satisfied themselves that my disability does not affect my ability to fly. I had to do a separate flight test with an FAA employed examiner to get this but it is effective forever unless my disability changes.
A friend of mine has checked with the insurers of his helicopters in his flight school and they are happy to accept me flying his Gregistered craft on my FAA license without any additional requirements.
However, I will check all this again and let you know. Also the
FAA are happy for people to train for FAA ppl(h) in the UK on G reg craft. I have had this confirmed by them.