I was going to suggest Matalan, I have some there from last year and they’re sort of similar to your picture but slightly less ‘haremy’ and more cropped jogger. They’re so comfy I bought two pairs. However I don’t see the exact pair on their website.
Before the Matalan ones I had an amazing similar pair from Tesco which I wore into the ground over a few years.
Have also had more expensive cotton pairs from Boden which are lovely but I like the stretchy knees on the cheaper ones.