Cheapest way to heat open plan?

[Pelo2022]

So I have this ridiculous layout designed by people that weren’t obviously planning for actual living
pic attached. I work in the area where the patio doors are, and the only radiator/heat for the entire room is under the living room window

The rest of the place is toasty, because the bathrooms have huge radiators
The living room never feels warm, and the kitchen area is chilly. What would be cheapest to run, or any other ideas to heat it up? Links welcome, I’ve been browsing Amazon and am lost in reviews
I can keep myself warm ish but I want to heat the actual room for visitors and mould reasons and the cat

If you were going to do major works then you really need more radiators there. But it could be quite a big job. We have similar, a really big open plan area with lots of big windows and we boost it with an oil filled electric radiator when we need to. It does the job. I can't link because it's really old.
We also have full length curtains for the patio doors which help keep the heat in.

Wood burner.

Is this a flat, OP? It doesn't look like you've got your own boiler on that plan so maybe it's not feasible to add CH radiators which otherwise might be the best bet.

We have a very large open plan space and ultimately we put in an extra two radiatirs and made them all doubles. As well as getting larger ones. So now there are 4 in total. Now it heats up lovely.
If the kids are out at school and I want to warm it while I’m in there and not put heating on I just grab my little fan heater and point it at me while I’m sitting working at the table.

It is, and own boiler (for some reason not on the plan but it's at the end of the kitchen)

In that case I'd definitely be looking at adding a radiator or two - may depend where the pipes run.

First pic shows boiler (upper cupboard)
I was wondering if it would work to have a radiator on the wall behind the high table
second pic is me standing in the kitchen and you can see the under window radiator
Its not helpful that its such a random shape!

definitely need a temp fix so if anyone can recommend a fan heater

Radiators running off your boiler will be cheaper to run but significant cost and disruption to install.
Fan heater for £15 under the desk. Useful in case heating ever breaks to have in anyway. Mine has a 1.2 or 2.4kw setting with a thermostat.