Does anybody know chapter and verse about whether it can be done as SNY (supernumerary) too?
I'm thinking about the situation where your PPL mate, who is acting as PIC (so you are just a passenger) is confident and gentle enough to let you handle the controls during take-off and landing.
I can see a few issues with this.
Firstly, assuming its an SEP (single crew), and your mate is not a flying instructor, you cannot log any time for the flight. You can obviously write whatever you want in you logbook (it's your property) but for CAA purposes, 'dual' time in a SEP means nothing. As RTN11 says you'd therefore have a hard time evidencing the flight and the landings.
Secondly (again assuming your mate is not a flying instructor) either you or he is going to be flying the aircraft from the right hand seat which presumably you have not been trained to do.
You might also run into insurance issues. In my flying club the only people allowed to fly the aircraft are group members, who have been checked out by a group instructor. If I let a mate take control there would be a very sticky situation if he bent the plane. I'd have a choice of either committing insurance fraud by pretending I was flying at the time, or admitting that he was in which case the insurance would not pay up.
The best bet if you're outside of 90 days is probably to go up with an instructor, or just bite the bullet and do three solo circuits (although the rule is there for a reason - flying is a perishable skill and currency is vital).