id personly prefer to buy a mask new, so a flex 8 or 7 would be a very nice mask, and for about £40 or so,
you can get a second hand steel air bottle in the classifed for around £30 (depending on how much life it has)
cant go wrong with a halo or reloderB, there about £35 or so second hand i think?
soo, we now have £205 for a marker, you could get a very nice PMR for that, an etek, shocker, SLG (second hand on the classifeds)
the best way to decide is to have a trip down to a torny or walk on, and ask some guys for a try of the stuff. or my personal favourite, a trip to BZ and spend about 40 mins trying out/on everything they have in stock