Grandfather rights...
There seems to be a bit of confusion here.
If you have a pre-2000 PPL, with an FI rating, you CAN be paid.
In order to receive payment for flight instruction, an
instructor must hold a valid professional pilots licence and
valid JAR-FCL Class 1 Medical Certificate.
Instructors who hold valid private pilot licences and valid
JAR-FCL Class 2 Medical Certificate are entitled to
instruct but cannot receive payment for this service*.
* This does not apply to the holder of a UK PPL(H)
who qualified prior to 1 January 2000 under national
arrangements
Boffo.