Our house is over 200years old. When we moved in 38yrs ago the only heat came from open fires and the aga in the kitchen. (flannels would freeze in the bathroom) Aga was kept going all year round for cooking and heating water (and reviving the odd half dead lamb in the bottom oven). We now have oil central heating together with open fires which are also designed to run downstairs radiators. Never have it on a timer, just turn it on when I get up. Our bedroom has never had the radiators turned on. Windows opened wide even in winter (last night wonderfully cold as a keen frost here). Not sure if it's the thickness of the walls but the rest of the house retains the heat pretty well overnight. Get through one fill of oil tank a year( 2300lit.)We have our own supply of logs for the fire (lots of fallen trees), we also supply MIL and son with logs for their log burners.