Thanks for this. The issue is we can only access one of the valves. The other is either right up against the wall or it doesn't exist. We can't get there to look and say for certain.
Are there definitely two valves? What would happen if we just opened the valve marked 1?
We're having issues with the pressure on our Potterton Performa 24 boiler, it currently stands at zero. When the water is turned on it goes up to 0.2 absolute max. We're having issues getting hot water in our bathroom because of this.
I'm attaching a picture of our pipes - I've marked the two...