I have a loud grinding noise coming from my roof,it sounds like someone is using a saw or a grinder (but I checked and there's no one up there!) its louder at night but I think that's because there's no other noises and I'm lying there listening to it
It's not the pipes because I run the taps and it makes no difference but I'm thinking it could be electrical. It's a 1960s single brick and tile house originally built for homeswest
Does anyone have any idea what it could be and how to fix it?

Flying squirrels, active at night, make a grinding/ gnawing sound when they are chewing on the wood, making a nest or trying to get in.

Flying squirrels? We have this grinding sound coming from our roof and we think it's more likely a failing turbine vent. It grinds now and then, erratically.

You have answered your own question!! There are bearings in the turbine that be making noise. If you wedge something either inside or outside to stop rotation and the noise goes away that is the problem. No wind also means no noise. Walt