(dd) no person acting as a pilot on such a flight shall be employed as a pilot by or be a party to a contract for the provision of services as a pilot with the operator of the aircraft being flown on the flight.
BEagle
The para you quote is tacked on to the exclusion which allows cost sharing for private flights. Since no cost sharing is taking place for the checkride in question -- the renter is PIC and pays the cost of the flight in full, carrying the check pilot for free -- (dd) is not relevant.
I don't think there's any doubt that if the check pilot holds a CPL (with or without FI rating) then the check ride is legal. Likewise, if the check pilot holds a PPL and is not paid, directly or indirectly, for the flight. The sticky area is where the check pilot holds a PPL and is employed by the club, and therefore it could be argued that he is receiving remuneration for the flight.
The paragraph (dd) above is required to prevent the following situation: A club rents out a PA28 for £200/hr, to be shared between 4 occupants. The PIC happens to be an instructor employed by the club, and receives remuneration of £70/hr for making the flight, but pays £50/hr, his 25% contribution to cost of the flight. Et voila: air taxi operation by the back door...
Of course none of this affects the status of trial lessons by non-instructors (CPL or not) which are clearly illegal before they leave the starting gate.