I'm 64 and my personal thermostat stopped working more than 10 years ago. I do get very hot at night, but have found that what M&S call "Comfortably Cool Mattress Protection" has reduced the heating effect of my foam mattress (which I use as it suits my dodgy back). I also use 100% cotton bedding and a 2.5 tog duvet for most of the year. If I'm very hot I sleep without the duvet - which is why I wear cotton PJ's.
I don't think there is any solution to this overheating problem, sadly, but I can live with it. More difficult than the nights are the days: if I take any sort of exercise (making beds, light gardening, walking briskly) I sweat profusely, looking as though somebody has tipped a bucket of water over my head. I get hot if I get even slightly anxious!
HRT seems like a sensible solution but personally I don't like taking any sort of medication if I can avoid it. The slightly elevated risk of cancer bothers me - two friends had rapid breast cancer whilst on HRT - and I think that I can live with the inconvenience.