my Ravenheat Combi boiler had a problem recently where it was on zero
pressure, so I turned a plastic tap underneath which was connected to
a felxible pipe, which seemed to let more water into the boiler.

The radiators now all work full heat, but the hot water isn't very
hot, and the hot water isn't hot at all when the switch is switched
from central heating and hot water to just hot water. I've tried
varying settings on both thermostats.

It seems like something's wrong as the boiler used to be fine to pump
out hot water when the switch is just set to hot water.

Pressure is about 0.8 bar cold and i'm not sure what it is when hot
but its over 1 bar.

Has anyone got any ideas please before I call out a plumber?

Many thanks.