Ethical thermal leggings

I’ve recently come to the realisation that as good as it feels to wear tights (+1 femme!), they aren’t anywhere as close to as warm as what I’m used to with men’s bottoms.

I’ve got some 120d tights from snag, and whilst they’re a good basic option, I’m after something warmer like thermal leggings. The easy option is primark, but having worked for them for a time a few years ago I have some misgivings with their ethics. Does anyone have any recommendations of at least ethically neutral thermal tights that would fit a 184cm (6’2”?) girlie like me?

I can work with in person if they’re in the Manchester area, or online if not. Thanks in advance!!