As already suggested, "a lot" to one is another's abstinence. It constantly amazes me how low a priority heating receives in a high proportion of UK households. More than this, people are constantly being encouraged to accept as a worthwhile goal to "save" by in effect switching things off. I recall visiting one family in winter where it felt decidedly cold to the point where at least one of the adults parked himself, standing up for a substantial part of the time, leaning hard up against a lukewarm radiator.
If people genuinely don't have money to raise the indoor temperature above the outdoors' that is one thing. But if the same people have money to pay for drink, tobacco, a recent car, etc., etc. then it is a conscious choice to be cold. A thermostatically controlled heating system is on 24/7 but reacts at all times to a drop in temperature, brings it up to the chosen level and then goes to sleep - it is not a luxury unless you prefer to spend the money on other things. The chosen level can be 15 degrees or 25 degrees. Elderly, the older you are (and less physically active), the colder it feels at any given level even past 21 degrees.
There may be room to reduce the bill for unchanged consumption by switching schemes or suppliers. The elderly neighbours may simply place greater priority than you on at least not shivering (or needing heavy outdoor clothing, wraps, etc.) in their own home and maybe they are not likely to find the bill for their consumption available for less than at present.
Depending on the size and type of accommodation, your neighbours may already be heating their home only minimally and thus the bill may be unrealistically low for anything resembling a comfortable existence. If my home (18-22 degrees 24/7) were heated using commercially bought electricity or fossil fuel, the bill for energy would (cheapest supply/scheme) probably exceed £1500 per year by a good margin. They may be aware of "savings" concepts involving switching off, down, etc. and not want to.