alphamatt, yes, that's indeed what I was 'on about'. Quite how he failed to understand is hard to see....
To fly an aeroplane heavier than a Microlight on an NPPL, you would need to add an SSEA Class Rating to your NPPL. Or, if it's an SLMG, an SLMG Class Rating.
The SSEA limit is 2 tonnes and 4 PoB (including the pilot). Anything more and you would need a PPL(A) with SEP Class Rating.