Thank you all for replying. Yes, Monica it is hyperthermia that my daughter keeps on about and and has sent me various articles.
Problem is that I do not feel the cold very much. Cannot sleep in a warm atmosphere, so heating is off at night and I only have a 4.5 tog duvet. My flat is quite warm, and only if it gets very cold at night -below 0 degrees outside, do I need anything in addition to that.
Due to mobility problems and COPD, I do not do a lot except for housework and cooking. Do about 10-15 mins of gentle exercise each morning. Otherwise I do spend most of my time in my recliner chair, on laptop, listening to radio, watching tv.
In the past, I would be going out most days to things like U3A meetings, but they are on zoom now.
So, yes, I will try to be more careful and put my heating on during the day and keep an eye on the temperature, not allowing it go below 18 degrees at any time indoors.
Wellbeck, I have Pension Credit and some Attendance Allowance. As I have no mortgage, although do have maintenance agreement for my flat, I can live well within that and really do not have to consider a little extra cost with regard to heating. If you are on just £70 per week total income, then you really do need to find out how you can top up that income.