pay £100 for combined FAA & JAA Class 1 medicals.
Well, then you're very very lucky !
AS for GPs and the NPPL, my only experience is two visits in 5 years, but I assume they do HGV medicals all the time, and if they can clear you to drive a huge truck - and probably live on all day breakfasts - they must clear you for this too.
On my first visit the GP hadn't heard of the NPPL, but I explained and gave him the reference sheets, and he understood. On my recent visit 5 years on a different GP said he'd seen a few of these, and just checked the computer. As I haven't been near the place in a long time, there was no reason not to sign, as it's a negative check. It's up to the pilot to flag up medical reasons not to fly if the GP doesn't have any.
B