This is the pneumatic system, still missing the cylinder... Used 1/2'' fittings through out. Not yet fully tested as I got no Co2 available yet But monday I'll get an expired fire extinguisher and I'll have a go at refilling the bottles (I'm slightly concerned as this is my first fill! )

Partially tested the system at 6 bar this week and it worked fine, removed the regulator and supply tank and connected an airline to the 5 way valve inlet, energized the solenoid and bang - QEV opened and there was a large flow of air from the T-piece just behind the QEV.

The pressure gauge on the buffer tank is just a temporary thing - to compare the pressure to the regulator when I go to 11bar with Co2