I also noticed in the manual for the pressurised thank that I can add pressure by using a bicycle pump on the valve on top of the red cylinder. But I know there is a lack of water in the system at present so I'm not sure that will help.
No - that's purely for pre-pressurising the expansion vessel.
Go for the hosepipe. All being well, topping up should not be a regular activity so it matters little that it's not as convenient as a dedicated filling loop.
Mathew
The low pressure is partly my fault. It was already low but I then opened the pressure relief valve when diagnosing other problems. I also bled all radiators which further reduced the pressure.
I will either use the hosepipe or may consider fitting a filling loop.
Any advice on fitting a filling loop? There is mains cold water available in the airingcupboard, but where abouts should I connect the other end?