As its not the first time its been mentioned, heres how I did my bottled set up, I stuck it in plants as that seems most appropriate
I bought a this regulator , this nut and tail , I got the bottle off him, a 12Kg bottle for £20, which I picked up off him - hes in Nottingham. To regulate the C02 you really need a Clippard MNV-2 needle valve and the tube adapters (I have a few spare) this valve costs about £8 I think, I managed to get mine for free, cannt remember the name of the company I got it from though....
As for the defusser, you could use the one from a Hagen DIY kit or a JBL one or use this Its Plantbrains design, so has to be worth looking at.
Apart from the above, you will also need some silicon tubing, not the white cheap stuff as you will leak c02 using the wrong tubing.
When you turn it on, the regulator only needs a tiny bit of C02 going though it and use the needle valve to fine tune it
OK, a year on and the bottle has run out, struggled to find a refill or a replacement bottle, so I contacted a fire extinguisher wholesaler and bought a reclonditioned 2kg bottle for £20, you should be able to get one from most suppliers, just ask them when the bottle was made though as the one above was made in 1966 and shouldn't be used anymore.....
Heres a pic, all you do it remove the tumpet, wrap ptfe tape (69p from a DIY shop) and screw the regulator mentioned above onto it. When you squeeze the trigger, the pin can be re-inserted into the handle so it stays open. Just make sure the regulator is closed when you squeeze the trigger or you will loose all the c02 and the bottle will fall over