Boiler kettling – It seemed that F1 protector it supposed to help with this, but it seemed putting that in caused trapped air and other nasty reactions.
Expanding / shrinking pipes – This sounds like it could indeed be the case. As I can lift and move my radiator slightly and feel it rubbing in the hole in the floorboards, and I can almost create the identical sounds myself by doing this. However, the radiators and pipes have not changed since our boiler got replaced, so as that is the case, I can’t understand why this should be related. Our heating with our old boiler just bade a very quiet and consistent tinkling while on, and no noise when off.
Dirty pipes – While we had the F1 protector put in supposedly to clean the system, given the reaction it caused, it probably has made it worse. We don’t have air / gas in the system now and the water seems clean, but I obviously can’t tell what the pipes are like. I don’t believe it is related to the radiators now, as I can turn them off at both the TRV and other valve and the noise still occurs from the pipes.