I live in Fleet, pretty close to you. I get C02 from Andover patio. They charge about ÃÂ£26. This is more than some suppliers, but you don't pay a deposit for the bottle. So get one or 2 bottles from them , then go get a refill from someone else at a later date.
The home brew shop in aldershot is also worth checking out... (No CO2, but everything else)