Pedro, sorry you have had your collar felt, but as said above you have learned a valuable lesson. having flown a lot in this area, given the proximity to the london class A, i am surprised your school didnt send you out with another instructor to point out the local landmarks, before you went up with a student.
if you can recognise wycombe, marlow and maidenhead, and you stay to the west, you will avoid trouble. the "november" joining point for WW at henley is, i am sure, there to keep joining traffic away from the class A. i suspect your club member thought he could fly a direct line between booker and WW, ignore the joining instructions, and get away with it.