At £18 per cannister (was last time I checked), it's a damn pricey way to go.
It's not so much that CO2 is less accurate, but CO2 guns (Crossman, etc) tend to be cheaper than precharges, and therefore less accurate. Also, CO2 pressure varies quite a bit with temperature, causing shots to go high or low.
Why don't you fancy a precharge? It's far cheaper in the long run.
HTH