I am sure it's related to the hot water system and started with teh freezing weather.
It doesnt happen all the time just short spurts of noises I can hear downstairs.
I assume it's not a leak as nothing has come through teh ceiling!
Our step ladder is at teh other end of teh garden and even with that I cant see the whole loft as I'm not good with heights to be able to climb in.
ANy ideas what it might be?