Hi another question.

I have a radiator or pipe leading into it which seriously bangs. Not all the time and it appears to be when the heating has been on for a long time - like today - and it is just ticking over. The banging is so loud as if something is stuck and trying to get through if that makes any sense. We have changed the thermostat as we thought it might be that but it hasn't made any difference. Any suggestions as to what we could try next.

The radiator is upstairs if that makes any difference. Thanks.