Help Topping Up Water Pressure on Vokera 20-80 RS Flowmatic!?

Hi there,

I've been having a few problems with my boiler (Vokera 20-80 RS Flowmatic), as we are able to get central hearing but we have no hot water. The water pressure dial is sitting at just about 0.5, so as I faced this problem in my previous home I was able to fix it by turning a valve underneath the boiler. I just can't seem to find the valve on this one! I've tried all of the valves underneath in the hope that it might be there but nothing seems to do it.

I have uploaded a picture of all of the valves underneath the boiler so perhaps it'll be easier to solve. The valves also have a strip at the back naming certain parts, so I'll just list it as it from left to right -

Return Safety Valve (In Front of Heating Return)
Heating
Flow
Gas Inlet
Hot Water
Cold water

The picture is at http://www.thewhiskyworks.com/boiler.jpg

Thank you very much in advance for help!
Ralph