Thanks Dave,
there isnt a drain on any of the downstairs rads, I had a look at the pipe runs as well, and there doesnt appear to be one there either.
the guage doesnt appear to be stuck, if i tap it the needle it will jump around quite a bit but always returns to .5bar, that said I suppose it could still be jammed inside somewhere.
If i remove a bleed from downstairs rads, then the water does come out of the bleed screws with a little pressure so i wonder if this is where the issue is (could it be an air lock) ?
If i pumped up the PV to 10psi now, and the needle does not move, would it be fair to assume that there is no water in the PV (otherwise it would either displace any water via the drain, or I would see a corresponding increase on the guage of around another half bar) ?
If I do this and the needle does not move, do you think i could then close the valves and bleeds, and refill to say 0.8 bar, then fire it up for a few mins to see if it vents out the air blockage ? and things return to normal ?
Many thanks for your patience and help
Cheers
Shaun