Public transport and aerial work - general rules
157 (1) Subject to the provisions of this article and articles 158 to 163, aerial work means any purpose (other than public transport) for which an aircraft is flown if valuable consideration is given or promised in respect of the flight or the purpose of the flight.
I think it fair to say that an examination fee is for the purpose of the flight!
A simple test is to ask would the fee be paid if the flight did not take place? If the answer is NO then it relates to the flight.
That precludes being remunerated on a PPL unless you are one of those PPL holders detailed in Schedule 8
Schedule 8 PPL Privileges
He shall NOT:
b) receive any remuneration for his services as a pilot on a flight save that if his
licence includes a flying instructor’s rating, a flight instructor rating or an assistant
flying instructor’s rating by virtue of which he is entitled to give instruction in
flying microlight aeroplanes or self-launching motor gliders he may receive
remuneration for the giving of such instruction or the conducting of such flyingtests as are specified in sub-paragraph (a)(i) in a microlight aircraft or a selflaunching motor glider
From AIC 48/2006
Accordingly, if an aircraft owner wishes to have a flying test conducted in that aircraft, the payment to the examiner will render the flight aerial work so that the aircraft would normally need to comply with the airworthiness provisions applicable to an aerial work flight.