That's the great thing about the forums. People trot out opinions or quote documents that may or may not be correct rather than refer to the law. The CAA bu@@ers about with the rules so much the only way to see what is correct is to look at the legislation.
ANO 2005 Art 11(4)
(4) With the permission of the CAA, an aircraft flying in accordance with a national permit to fly may fly for the purpose of aerial work which consists of the giving of instruction in flying or the conduct of flying tests, subject to the aircraft being owned or operated under arrangements entered into by a flying club of which the person giving the instruction or conducting the test and the person receiving the instruction or undergoing the test are both members.
ANO 2005 Art 11(1)
11 (1) The CAA shall:
(a) subject to sub-paragraph (b) issue in respect of any non-EASA aircraft registered in the United Kingdom a national permit to fly if it is satisfied that the aircraft is fit to fly having regard to the airworthiness of the aircraft and the conditions to be attached to the permit;
(b) refuse to issue a national permit to fly in respect of a non-EASA aircraft registered in the United Kingdom if it appears to the CAA that the aircraft is eligible for and ought to fly under and in accordance with a national certificate of airworthiness.
Mike