Shut that door

When a room’s not in use for a long period of time, if the kids are at Uni for example, turn off the radiator valve(s) and close the door. You’ll be saving energy and keeping the warm air in the rooms where it’s needed. BUT, if a room’s in regular use, turning off radiators completely is less energy efficient as your boiler has to work harder to increase the temperature again than if it was kept at a low setting.