It is definately cheaper to do pressurized CO2 individually rather than a complete system (in most cases).
My CO2 system is:
Tank (5lb)
Silicone Tubing - they say CO2 proof tubing is best but this has worked for me.
Regulator - purchased at
Morebeer Regulator. You will have to find one similiar that will fit non North American CO2 bottles. Check welding business as well as places that sell make your own beer products.
I did not like the turn off valve so I went to Lowes (or local hardware store) and spent $10 to get a good metal ball valve that feels good. This is optional.
Needle valve is a MUST - I forget which one I have but read that the one at aquabotanic is good (#mnv4k2).
Bubble Counter - from bigalsonline works from me - I think it is the AquaMedic one. I opted for an external bubble counter.
Custom diffuser on canister output - instructions
Here. This is external as well, but there are internal ones as well.
Tank $60
Regulator $55
NewBallValve $10
NeedleValve $20
Bubble Counter $20
Tubing $5
Reactor $15
This yield $185+various shipping including tank (~102£). This is also external. Internal CO2 systems will be cheaper (in general).
Also look at
this
Milwakee Regulator. It has Regulator, Solenoid, Bubble Counter and Needle Valve all in one. I have NOT used this one but have read fairly good reviews about it. Again I think this is for North American bottle standards.
HTH a little bit
Aries