Don't forget that it is a requirement that both the instructor and the student are members of the same club. being a member of the club gives you more rights than being just a customer.
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I don't think that you would get very far with that because;
a) The holder of a JAA instructor rating (even if included on a PPL) can instruct on microlights (after appropriate differences training) and thus can be paid more than the average CPL holding instructor.
Regards,
DFC