Energy efficient and safe electric heaters

I’m changing the heating in one of my rental flats and wondered if anyone has recommendations for energy efficient, safe electric heaters ideally as slim as possible as they will be wall mounted. (there is no gas or central heating at the flat). We had standard convector heaters but I’m sure there are newer more efficient and safer options available now. Any feedback or suggestions appreciated. Thanks.

You will only get a decent EPC rating with storage heaters.