Hey Guv,
As far as I'm aware, the only differential in limitations an 'NPPL' imposes instead of a 'JAR PPL' is that flight may occur only by day and within the United Kingdom. I can't see why it would resrict one from flying something like an Arrow or other complex, although someone feel free to correct me if I'm wrong.
When it comes to weights however, it's probably worth checking the UK AIP.
Cheers, Jack.
