I am a big believer in cashmere, particularly for hands feet and neck as that seems to keep me warm more broadly. Although I don't find cashmere socks that comfortable so am more likely to wear hiking socks with boots (a size or half a size up on my regular size so they fit) or those super fluffy socks that are more like bed socks - but they're not as comfortable when wearing shoes.
I always always wear a close fitting vest - I have a few thermal ones from places like M&S, John Lewis, Uniqlo. They don't work in isolation, but I find them a good base layer. Then a long sleeve t-shirt or similar, then a cashmere jumper is, in my experience, the best for trapping the heat in (wool is massively overrated for me). I actually find they're warmer with a t-shirt rather than a long sleeve t-shirt but that might just be becuase I have mild sensory issues and double layers on my arms have always been a trigger for me.
I have had good success with heavy padded coats from Trespass - and they're often reasonably priced and/or on sale. Longer ones are better as they cover my thighs which suffer.
Cashmere scarf ALWAYS. If you are really struggling, a thin silk (not one of those "silk" scarfs that is satin - it must be proper silk. You can get a good selection at reasonable prices on Etsy and sometimes at Accessorize/Monsoon) scarf UNDER the cashmere scarf works well - silk is surprisingly warm in that it traps heat.
When it's especially cold I wear thermal leggings under thick denim jeans, hiking socks and proper boots (the last few years mine have been walking/hiking boots also from Trespass but I've had from other places too. Weirdly, had a good pair of padded boots from Sainsbury's for a few years which, with my hiking socks, were surprisingly warm).
At home, we've abandoned feather/down duvets. The more solid ones from Ikea or similar are a LOT warmer and don't need 30 minutes to get warm in the first place. Electric blankets - either under sheet in bed or a fluffy one for sitting on the couch - are a godsend.
I wear slippers at all time - always in boot form. I've been wearing Bedroom Athletics ones for the last couple of years. The best I've ever had were from The White Company - but they don't do them every year. they did them 2 years ago but don't seem to have done them again recently.
Good luck. I feel your pain.