Further to this the UK CAA cannot give approval for a pilot operating on a valid ICAO flight crew licence in a UK (G) Registered Aeroplane in another ICAO or even EU(JAA) States airspace.
As such, authorisation must be sought for any non-UK or non-JAA pilot wishing to fly a UK (G) Registered Aeroplane to say France, or other mainland European Countries.
I think Mr Willcocks's response contradicts the ANO. The passage above does not follow logically from the rest of his letter.
Art 21 of the ANO renders valid an ICAO licence for use in G-reg aircraft (with the restrictions described) without territorial limitation. Other states are obliged to accept this validation by Art 32(a) of the Chicago Convention. JAA has nothing to do with it.
While the CAA may direct otherwise in particular cases, it is not within their remit to reinterpret the statutory instrument.