You got me there, c172driver.
Obviously there are several interacting considerations:
1. Under the FARs, as a BFR "training"? I think every flight with an instructor is, but it may indeed depend on what purpose.
2. Can a pure JAA PPL really instruct at all (i.e. provide instruction which can be logged in any way)? I am not convinced that comes out of the debate in the other thread. If this were legal, there would be positively loads of PPL "instructors" freelancing all over the UK, charging for "ground school".
3. The requirements of the ANO for foreign reg planes, and what sort of stuff the DfT will allow.