These jeans are a really nice quality stretch denim. They’re not super thin like some stretch denims can be, but have enough stretch to move with your body and in general are well made. Love the green colour too!
I am a UK size 12, 31 inch waist, 40 inch hips, 5ft 1” and normally get anywhere between 29-31 jeans. I got the 31 regular this time as it was all that was in stock, and it was far too big for me in the waist. Too big even for a belt to fix. Length-wise I found it to not be too bad, and the fit on my legs was nice, but you can see how baggy the material is around my waist in comparison to everywhere else. So if you are a similar size to me, a 30 or even 29 might be a better bet.
Despite the sizing, I still think these jeans are great and would want to get a smaller pair. Current returns are free so that helps!