I have bled a radiator, which has drained the pressure out of the system. I now have an F1 error message, which is not included in the manual - as it only starts at F2.

There is no apparent pressure gauge, but there seems to be a pressure valve. There is a Mag Defender canister under the boiler, but I do not know what this is for.

David Davies, November 2015

Slight correction, now that I have done this.

There are actually 2 black handled levers underneath the boiler, alongside the pressure gauge. The blue handled one is the water inlet for the dishwasher.

Still, problem solved.

Jason of One Stop Eco Shop, November 2015

A very nice man has 'phoned me with the answer, without the need for a callout.

The pressure gauge is underneath the boiler, and there are 2 taps. The one with the blue handle on the right is the one that recharges the system, and the one with the black handle to the right of this only needs a tweak whilst the system is filling.

Jason of One Stop Eco Shop, November 2015