Hi again. Review of the twist-top version:
Fabric is a good-quality matte lycra blend, lightweight but not sheer, nicely finished with no ragged edges or loose threads.
I currently wear a UK size 20 -- at M&S, anyway -- and was advised to order the XXL. I'm happy to have done so because the rise is just right; it would have been a little hazardous in the back had I gone down a size.
I like the fit on these pants VERY much because they skim the thigh and fall from there, rather than grabbing down to the knee and then flaring out sharply below. Lower leg has a straight hem: no lettuce edge, no slit. It's full enough to be good and swooshy but not so full as to trip up your neighbors.
On me (5'5" and wide) these pants are are floor-length but don't puddle, so they should also work well for someone taller and slimmer. (Which is, hmm, just about everyone really.

)
If I've missed anything you need to know, just ask. And if you try the glitter-waist ones, please report back because I want those, too.
Best,
Suzana