Fine to start with an NPPL(M) but (from LASORS):
"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)."
So 100 hours of NPPL(M) time will give you 10 hours towards PPL(A) - not a good conversion rate for your money spent, unless your NPPL(M) hours are almost free.