I have a friend who is doing the NPPL on microlights and I believe you need to convert it to the PPL. He said it was around 21hours you need to do to convert it to the full PPL (I may be wrong).
I don't think your attitude will help you at all, you cannot start off doubting your skills as instructor before you get there. What you should be aiming for is to become the best instructor in the world
Best of luck!