Landlord refusing to replace heaters despite maintenance saying it's required.

I've been freezing this entire winter, I moved into this flat in June last year and it's mostly been fine, however as soon as it started getting cold it became obvious the heating is an issue.

There is 3 electric heaters total, 2 in the living room, and a small one in the bedroom.

Out of these, Only one in the living room actually gets hot, and it only gets hot when it is set to max heat, max boost. I cant have it on longer than 30 minutes else it feels like im cooking while near it (It's right next to my work desk so I can only handle it so long and I'm worried about stuff near them being damaged by the intense heat), the other living room ones temp cant be changed, it's boost doesnt work, and funnily enough it's power switch doesnt work (the only way you can turn it off is via the fuse, not the on/off switch). Finally the bedroom one, It just does not work at all.

I reported the issue at the end of Nov, and it took until 20th of Jan for engineers to come out and look at it, which they said immediately that the heaters are extremely old (30+ years) and need replacing and left without doing anything to them.

I got a confirmation email today that the issue has been resolved, I asked them when they were going to be replacing the heaters and they said the landlord has decided to not replace them.

I dont know what to even do now, I'm so sick of waking up freezing cold and battling the cold constantly throughout the day, I feel like I'm wearing more layers inside than outside.