under the boiler on the left hand side there is a black lever push the lever you will hear the pressure dropping,do this till your pessure gauge is down to 1.5 it should be ok then
jonathan, February 2009
If you are not confident using the boilers' facility
just find any drain cock near a radiator and carefully open it to spill some liquid into a container.
Or just do the same thing at a radiator bleed point.
Beware HOT liquid
Best done cool
Regards