I'd say heat the person, not the space. Following on from the Electric Blanket mention, I'd recommend a heated vest. I have one made by Arris [1], and it has a 7.4V battery. Following a tip in an Amazon review, I
contacted their customer services and got a voucher for a second battery at half price.
Last winter, I used it a lot when WFH to avoid the temptation of using the boost on the central heating. With two batteries, one can be charging while the other is in use. According to my meter plug it was economical to charge.
I found it worked best with a thin base layer underneath the heated vest, and a good fleece over it. There are several heating areas on the front and back, and I found that the battery lasted best by starting at the highest heat setting and then stepping down through the levels as I warmed up. Very useful when sitting still long periods at your computer. And of course the advantage over a blanket or electric fan is that you can walk around with it on.
[1] https://www.arrislife.com/products/arris-heated-vest-size-ad...