It’s all very well to say heat the person not the room…the issue is hands. I get very cold hands that make me feel so cold…you can’t put gloves on and still beable to do anything. I stitch and read when at home …coldhands make stitching impossible. I’m retired and sitting wrapped up like a mummy all day is not practical!
the other thing to look at OP, is to forget electrical heating and instead look into smart radiator thermostats . As others have said gas is cheaper.
you can then set individual temperatures and schedules for each room. So get more heat into sitting rooms, less into halls etc. I have upstairs switched off most of day for instance. But can easily turn on form app if I decide I want to go upstairs to crafting room that day. I heat bedrooms warming in morning, and cooler at night as can’t sleep in hot room. I have kitchen diner warm at breakfast, then lower during rest of day when just flitting in and out fully dressed. And I can focus heat in sitting room where I’m most sedentary. I even set different schedules n different days of week dependant on when I have stuff I regularly attend outside the home.
you do need to go back to old practice I grew up with before central heating, which keeping doors shut so rooms are thermally isolated when you’re heating just what you need.
You need a plumber to put in new receiver etc on boiler and put new valves in.
The kit isn’t cheap, but I love the flexibility and know most of time I’m heating the room I’m actually using. The app ( hive in my case) is great. I can switch heating on or up easily on my phone, I can also check if I’m feeling cold genuinely because it is cold in room or I just need to move about a bit 🤷♀️.
bills are significantly lower this year despite having a warmer sitting room during day. I have more piece of mind to know I’m only heating where I need and warm hands!
have a look at that in terms of costs, but if mum isn’t good with apps it’ll not work for her.