Hi!
I’d suggest this kind of heater - radiant heat instead of convection means the person feels the most warm for the least amount of energy used. Also, this has three 400W elements to it, so you can only have on as many as you need. I use it to heat the ‘main part’ of me (torso/head), with big thick warm hiking socks on for my feet and a double layer of PJ bottoms 
I’d agree finding a way not to have the central heating on seems sensible.