Following DFC's comments (posted same time as my own!)
DFC If in moving the aircraft and student from the unlicensed airfield to a licensed airfield, the Instructor is paid then in my book, that initial flight is public transport since the pilot is being paid to carry a passenger to another airfield. Same goes if the instructor is a PPL instructing for free but the student pays.
aha. Interesting. I suppose the fact is that if money changed hands in any way for the transit flight with either the instructor/student or both then it is public transport. Makes sense.
Very Very interesting. Cheers once again for a stimulating discussion - especially as these sorts of situations crop up all the time in our instructor lives - its like instructor on group owned/private owned aircraft on a private CofA or Permit to Fly...but thats another storey Im not 100% clear on yet!!! Maybe another thread!?
Cheers All.
FF