To be honest, not sure what position valve was in when I refilled - but the rads appear full and drip when bled from the top, so assuming OK.
Have tried the central screw on the pump - and the air vent near the cylinder also drips when bled.
I had to drain my heating system to fit a new 3-port motorised value as the old valve had sprung a leak. This fitted fine and appears to work. However, on refilling the system I appear to have air in the pipes (microbore). The radiators are bled but when the boiler runs for a couple of minutes...