In which case I stand corrected, I do recall reading something similar though.
I am not a lawyer and don't understand the jargon but rule 28(2)c would seem to preclude passengers "having a go"?(sorry for poor copy/pasting)
28(2)c. not act as pilot of an aircraft in respect of which the flight crew required to be carried by or under this Order does not exceed one pilot if—
(i)the aircraft is not flying for the purpose of public transport or aerial work other than aerial work which consists of the giving of instruction in flying or the conducting of flying tests;
(ii)he so acts in accordance with instructions given by a person holding a pilot’s licence granted under this Order or a JAA licence, being a licence which includes a flight instructor rating, a flying instructor’s rating or an assistant flying instructor’s rating entitling him to give instruction in flying the type of aircraft being flown; and
(iii)the aircraft is fitted with dual controls and he is accompanied in the aircraft by the said instructor who is seated at the other set of controls or the aircraft is fitted with controls designed for and capable of use by two persons and he is accompanied in the aircraft by the said instructor who is seated so as to be able to use the controls;