Also, I doubt you'd get your GP to sign a NPPL med cert for £10 if it's anything like an HGV medical, which I've heard it is. Currently, £60 is about standard for an HGV medical.
I may be on wrong on this, but it would have to be an utterly simple form for a GP to charge only £10. GPs are getting more and more militant on private fees, feeling they have been grossly undercharging for years and years. You have been warned.
QDM