Regarding the update of an NPPL to a PPL this is not possible in my case due to medical reasons. I believe it it this reason, rather than cost, that most people opt for the NPPL.
Depending on what the medical condition is (I don't want to pry), then you should investigate the FAA route if you want more than a NPPL, which is very pragmatic when it comes to medical certification. As the FAA PPC is a full ICAO certificate there is noting from stopping you from flying IFR if that is your desire. You can also fly G reg aeroplanes without formality.
You can find a list of approved medications / conditions on the web, and you'd be surprised what illness you may have but can still get a class 2 medical certificate.
Interestingly Viagra is an approved medication, the only stipulation is that it is not taken within 6 hours of flying.....
