Does it have a thermostatic radiator valve?
It is the valve at fault and will need changing - it is hammering against the flow of water.
To use it until you get it swapped then either run on full or off
I think you may have to go around the house and turn them off one at a time to find the faulty one.
I think you are unlucky that they have started acting up, but they all tend to go at the same sort of time once they have been in for 10 years or so.
If you turn the valve down to shut it off or turn it right up it will stop banging until you get them swapped
Can you turn off the radiators one at a time?
Yes, no rush - lets work our way around the system
Does the pressure gauge needle vibrate when this occurs?