It's the only sensible way really.
Check out Aquarium Gardens, any of the CO2 Art regs they have will be fine. Quality at a decent price, and fantastic sales and after sales service.
Aquarium Co2 Kit from Aquarium Gardens. Includes Co2 Regulator & solenoid, bubble counter, diffuser and Co2 tubing.
www.aquariumgardens.co.uk
Pro-Elite Series Complete Kit is the highest quality CO2 System available in the aquarium market. This CO2 System is a combination of our best
www.aquariumgardens.co.uk
If they're in date they can be refilled. If not trade them in or give them to your supplier to be recycled or reused.