Some good info here (apart from the "avoid CO2 like the plague bit" - that's nonsense.)
Thing to do is decide what MAIN use your pistol will have - then make your choice. 'Formal' precision target shooting at 10Mtrs/6 Yards means something quite different to pure 'fun' shooting and timed comps (like Police Pistol or IPAS) for instance.
There's a huge choice if pistols to look at, from reasonably cheap to outrageously expensive PCPs and a whole range of repro vintage guns. Be warned though - pistol shooting is seriously addictive!
Have a look at the UMAREX Boys Club competition site for an idea of the various 'classes' that people enter in at the monthly comps. I have a go at many of those. There's a link here >> http://ubccompetition.btck.co.uk
Above all, have fun
FAS 604, Remington 1911, Colt SAA, HW45, BSA Mercury, Winchester underlever (Walther), SMK QB78