I bought two pairs from Peacocks last week - they're either £18 per pair or £22 for two pairs, I got one pair of indigo and one normal denim colour.
Wore the indigo ones today and they are sooo comfy! They look like denim, but are stretchy so they move with you, and they're lined as well so aren't stiff, and because they're tight they tuck nicely into boots.
And no sagging at the knees - bonus!
Just looked online and these are the pair that I wore today.