...not sure if this is the right place for this thread but I have a radiator in one room in my house that doesn't heat up as much as the rest. I've tried bleeding it (as well as all the other radiators) but there was no air to come out of it.

Any suggestions as to what might be the problem?

somebody has turned it off with a spanner at the opposite end to the operational valve?

Is it upstairs? Could it be that your 'loop' needs filling up because the heated water in the system isnt enough to reach that radiator?

Thanks for your responses guys, will check it out.