A few weeks ago British Gas serviced the boiler. Not my idea. Nice young lady who left me a leak on the Magfilter. Since the service we have noticed that the house takes a LOT longer to warm up. Before the service the place was warm in a couple of hours. After the service the house took about five hours to get warm - with the boiler running of course. The rads were hot, but not as hot as before the service. I suspected that she had turned the temperature on the heating side of the boiler down, but was to lazy to check as the boiler is in the loft. Today I had a look. From 3/4 she had turned the temp down to 1/2. She did not tell me that she had done this. The temp setting had been on 3/4 since the boiler was installed eight years ago. I turned back up to 3/4 and the house was warm in no time, rads very hot.
Would I be correct in thinking that two hours running on 3/4 uses less gas than five hours running on 1/2? I never thought to take a meter reading.