Sniper - probably save 30 more quid and get a G&G cm 16
You won't find any GOOD sniper at 100 pound. You need to upgrade most things in a sniper.
Though you could buy the base of the gun for 100 pound, a jg bar 10, compatible with TM upgrade parts. You'll need to upgrade a lot, pretty much everything, lots of guides on what to upgrade.. But will then cost you maybe 250+ quid on upgrades.
Though is fun when you get it going.