Hmmm... interesting if perhaps academic.
The whole issue is mixed up with the fact that most schools dislike any PPL, never mind a PPL/FI, taking "their students" up. If a PPL/FI works free of charge (which he has to) that just robs their remunerated instructors of work.
I can't see
any school being happy with this - unless the whole place runs on free instruction.
Incidentally, can any JAA instruction (by "instruction" I mean a flight which the student can log as PU/T) be done outside a flying school (an FTO)? If not, where is the reference for it?
Of course, anybody can go up with a PPL and learn from it; he just can't log it. And he better not tell his school about the flight, either