Socks!

I have been on a similar quest and have finally settled on a particular version of Heat Holders which I got from Ebay.

https://www.ebay.co.uk/itm/393735045233?hash=item5bac700071:g:AyUAAOSwtnRgtMMz

When they arrived they had a Matalan label on them so I guess you can get them from Matelan. I turn the top of them down and they still don't strangle the ankle. You can get some Heat Holders that are not so good so I only recommending this version.

I've bought these over the last couple of years and been happy with them.
Company changed hands not long ago and not too sure if they've changed comopositions.
https://arbonsocks.co.uk/product/exmoor-sock-british-made-luxury-wool/

I tend to look in 'outdoors' type shops, I find generally you get quality and they do what they say they'll do. A bit more spendy though.

Bridgedale are a good brand. Mountain Warehouse and Go Outdoors are good shops.

I have trouble with the old feet too! I have tried all sorts of socks to try and keep warm.
I bought some ski socks similar to the ones in this link At that price they are worth a go. The ones I got did have a percentage of wool in them but they are out of stock. They have plenty of good reviews but like my books, they keep the poor ones at the top, front and centre. (There is also a link on that same page to some wool thermal socks which I haven't tried.)
They were bought for cycling really but because they are ski socks they are better at going down hill!
Because I have chunky calf muscles (!) through lots of cycling and walking they were tight below the knee. So I got the scissors out and chopped off the elasticated bit. I now have four pairs of very warm ankle socks to lounge about in.

I recently bought a single pair of 'proper' walking ankle socks from a mountaineering shop in Kirkby Stephen. They cost £20 (!) but they are great walking socks.

I suggest that controlling your blood sugars is the most important bit.

Heat Holders have my vote too
Carol

I have bought Corrymoor socks for years. They do a soft-top version which is ideal if you get swollen ankles. It's a small company with its own herd of Angora goats, so very animal welfare friendly. The socks are a little more expensive but last for years, wash without fuss and are lovely to wear, soft and warm. Highly recommended.

I knit myself socks when watching TV - I have some Nylon ones I made 50 years ago still going strong but these days I prefer a yarn with a high wool content.
Some people seem surprised at there being no actual pattern, but just try them on from time to time. I work toe up on fine needles but transfer the stitches to a long circular needle to try on the sock. I do make a note of the number of rounds so I can get the second sock the same, or almost so, when I change yarn.

I wear Tradie socks, they are long wearing works socks.

https://www.tradie.com/mens/socks.html

Diabetes Queensland have diabetic socks including copper in their online shop.

https://diabetesshop.com/collections/circulation-socks

Or simply wearing 2 pairs of socks at once works well. The layers trap more heat.