I'd suggest start with the NPPL because it will allow you to get airborne under your own supervision quicker than any other route. Which route you take doesn't really matter - SEP / Microlight / SLMG, it's all flying and all fun.
As I say, get yourself airborne, do some flying, do some learning on your own, then you can think about upgrading to JAR, switching to another class of aeroplane, etc.
I know a couple of the instructors at the Microlight school at Medway (01634-270780) who all seem friendly and professional if you fancy starting with the NPPL(microlights) route. I've also dropped into Lydd for lunch and found myself chatting with some of the instructors there (which would be SEP) and was similarly impressed.
G