Hi mate, the obvious things would be getting it breathing better first with an induction kit, something like revo's or pipercross or vwr's one!
Then get an exhaust system, try and get a turbo back with either a sports cat or a decat. Something like milltek or bcs.
Then finally a remap, but you'd probably want a stage 2 as they're the closest thing you coukd get to 300bhp. Something like revo, apr, or superchips bluefin. Although i'd say revo or apr are the best!
Buuuuut, you might need to upgrade your clutch once you go stage 2 as it's more likely to slip with the amount of torque you'll have! Best thing i've ever done remapping a car though! 👍