My salon used to be freezing in winter as we have a big space and one wall is shop window. I installed an expensive German radiator under my window believing their calculator which said that would be all I needed - but it just wasn't. We ended up huddled over 2 kilowatt portable heaters which looked scruffy and we were still really uncomfortable.
Last winter I installed ceiling mounted infrared heaters which my brother supplied and fitted. They are fantastic, they are just slim white heaters which you don't notice at all. They're not heavy. The heat is very controllable, i have a room thermostat and I just flick it up or down 0.5° to tweak the comfort level and it takes effect within 10 mins. I've saved a lot on my heating bill and I don't have clients looking uncomfortable at our manicure desks.
Infrared heating is very efficient. I get more heating effect out of a 900Watt infrared heater than a 2kilowatt oil filled radiator and I don't need to switch it on hours before we open. I've recommended them to everyone I meet. Infrared heat penetrates into solid objects like the walls and floor and warms them. This means that even when the air temperature is a bit nippy, you feel warm, because the walls are warmer than the air. The've saved me loads on my electric bill and we feel much warmer.
They last for 20+ years, there's no maintenance and the installation is mess free and quick. You can take them with you when you move.
My brother is called Philip, his business is
https://goodlife-heating.com/supplies and he installs all over the UK. He's very helpful so he'll give you advice about whether this option will be right for you.