I'd say the noise has only been there a few months - 3 at most. Otherwise- the system is red hot and seems pretty efficient. It is quick to get to temperature and radiators red hot - and otherwise quiet... Really odd.
Have turned down teh boiler temperature a fair bit to see if that helps...
Thanks for the suggestion. Don't think it is that, though - as I only have a thermostatic valve on one radiator (en-suite towel radiator) which has been there 4 years - and doesn't seem to be the source of the noise.
I wonder if anyone can help with suggestions on how to solve a strange noise in our central heating system. This seems to have appearred/grown worse in the past few months.
We seem to get a kind of grinding/pulsing noise that slowly grows in intensity over a few minutes and then very quickly...