I've flown an ex-ATC Sedbergh glider in full Air Cadets/RAF regalia in France, Germany, Austria and Lithuania without a word being said by the locals (other than "can I have a go?").
But on the form which you have (of course) obtained from the RAF giving permission for military markings on a civil aircraft it does say amongst other things:-
"UK Residents" - The aircraft may only be flown within the airspace of Great Britain.
"Failure to comply with any of the above conditions will normally result in the authority to carry military markings being withdrawn"
I think the key point is item d) "The aircraft must not be flown in any manner which may cause criticism of the Royal Air Force"
