Re: NPPL to JAR-PPL
"See, this is just what leads to confusion: 20 hours dual and 10 supervised solo is 30 hours - so, an extra 5 hours must then be completed on SEPs to make that minimum 35."
Correct. The other 5 hours can be either dual or solo if you are given credit for flying in other classes of aircraft, othewise it must be an additional 5 hours dual conducted with a JAR authorised instructor.
"And then an extra 10 hours 'flight time' must be completed to make the 45"
No - it means flight time as credited for previous experience on other aircraft:
Holders of pilot licences or equivalent privileges
for Helicopters (including UK QSP(H) with no
previous SEP aeroplane experience), Microlights
having fixed wings and moveable aerodynamic
control surfaces acting in all three dimensions,
Gliders, Self-Sustaining Gliders or Self
Launching sailplanes or gyroplanes, may be
credited with 10% of their total flight time as
Pilot-in-Command in such aircraft up to a
maximum of 10 hours towards a JAR-FCL
PPL(A).
"....can we assume that that the extra 5 hours can be completed as a holder of an NPPL unsupervised, and what constitutes 'flight time'?"
Yes. Flight time means as PIC or Pu/t and is from the time the aircraft strats taxying for take-off until it finishes taxying after landing. So it does NOT, for example, include ATC air experience flying.