in the £150 what are you looking to buy?
marker, air bottle and loader?
at first i would recommend a steel 48cu 3000psi and this will cost £40 new
for loader i would recommend the proto primo i think it is, a very good gravity fed loader as it has a shelf which helps alot and feeds 8-9 bps
thats £10 ish new
thats the tank and hopper for £50 from justpaintball
and then you can get a decent second hand marker off of here for £100.
depending on what gametype he wants to play you should get different types of marker:
woodsball only - mainly woodsball markers (tippmans, bt etc) or maybe a speedball marker (if he likes shooting fast and having a light gun)
woodsball and speedsball - speedball marker