for that money i'd suggest going completely second hand to maximise your budget.
Hopper: 2nd hand Halo, Vlocity
Tank: 2nd hand 3000psi 68ci
Gun: 2nd hand BT-4/Tippmann 98
Mask: 2nd hand proto switch
This might even still stretch £100 but its the best you'll get. in all honesty i'd save your money until after the xmas period and spend even just an extra £50-80 and you'll be able to get much better gear.