I turned my central heating on today for the first time this year. The
bathroom radiator (the highest one in the house) feels like it has more
air than water in it, but opening up the valve to bleed it doesn't seem
to have any effect. I had the combi boiler serviced during the summer
and noticed, after the engineer had left, that the pressure had gone
down from 0.6 bar to 0.1 bar. Does the pressure need increasing before
it will be able to force the air out of the top radiator? How do I do this??