DRZ would be a good 1st bike, especially if you have to travel quite a way on the road to get to the green lanes you want to ride. Although it's a 400 it's quite tame. Other bikes to consider of this type are the Yam TTR250 or the Hon XR's. If you're short in the leg, there's a few bikes that would suit, like the Serrow or CRF230.
You could also look at the 4-stroke 250 enduro bikes (Yam WR or Hon CRF) which are lighter (easier to pick up
) & more offroad focused (handy if you live near the green lanes). They're very user friendly.
Are you aware of the recent changes green lane access?
I'd suggest buying TBM (trail bike & enduro mag) as it's full of useful info. It's quite hard to find though (A5 size). They also have a website & online forum:-
http://www.trailbikemag.com/