M&S cotton-rich sport socks, bought in packs of four or five pairs, can’t remember, but I’ve been wearing them for many years, always black, that way if one wears through I just wait for another to do the same then I’ve still got a complete pair! I’ve got some I’m still wearing that must be ten years old, at least! They always stay up, and they’re really comfy, especially as I’m on my feet all day, wearing steelies, and walking up to five miles or so each day – I need socks that don’t bunch up. Or fall down, either, and those don’t.
It’s these, I think, their Cool and Fresh range, five pairs for £12
https://www.marksandspencer.com/5-pack-cool-and-fresh-cushioned-sole-socks/p/clp60089758?color=BLACK