Hi, thanks for the reply.
I've switched all radiators off at the thermostatic valve apart from the faulty one and switched the heating back on full.
The boiler makes a noise like water swooshing round but the flame doesn't kick in at all. I opened up the radiator valves and the flame lit back...
Recently fitted 2 x downstairs radiators which are working fine, only problem is 1 of the 3 radiators upstairs no longer heats up at all.
Tried bleeding all rads and they're full of water but just 1 isn't heating and neither are the pipes going into it.
It's a combi boiler fitted on the 1st...