I leave the stop cock open on the filling loop - so that any water
that the system loses, due to the pressure release valve, can be
refilled easily - so the filling loop is always open - is this okay.
There is still not enough pressure.

The pressure release valve doesn't operate until the pressure is well
over 1 bar.

I'm not sure what kind of boiler I have - I'll check it and post it
soon.

Thanks again for the reply

Rob