The difference between the typical £100 every year for a 50+ pilot to an AME and poss £10 to get your GP to countersign your self-cert medical is significant
Is it really? I'm not saying £90 is a trivial amount of money - of course it isn't. However, it's only an hour in the air in the south of England, so it isn't going to suddenly unlock the door to flying as a hobby. I guess that there may be people who feel happy that they're competent and safe when logging the minimum 10 hours (or whatever) a year, and may be able to manage that with an NPPL but not with the extra costs of JAR, but I doubt that there are many. Sad truth is that you have to have a reasonably large disposable income to fly in the UK, and while scrapping AVGAS duty may change that I don't think the NPPL does.
However, please don't think that I'm knocking the NPPL - I'm not. I would like to add an IMC (ideally an IR, but cannot afford that) and I'd like to fly in the USA (my father-in-law owns a Bonanza
), but that's the only thing keeping me from the NPPL - and both of those will probably change in the future. There's also the rumour that EASA will hand private flying back to the national authorities, so we may all end up with a NPPL....