dont get CO2...
If youve got £200 solely for gun and air, Id take
1) Ion (good starter gat, can be upgraded later)
2) 4500psi 1.1l Air (youll be kicking yourself in a tourney with a 3000psi)
Ion you can get for £100 - 120, just be patient.
Youll get a used air 1.1 4500psi for £80 on here
Cheers