Ordering online and choosing sizes

[HareTodayDragonTomorrow]

I want to order a skirt. Waist measurement puts me at size 10, hip measurement at a 12. Bust measurement puts me at an 8, but that's irrelevant here.
How do you choose which size to go for? I've a dress from the same brand in an xs, but that's not much help. Ordering both and trying on is not an option (tax limits, return postage etc)

[BigGreenOlives]

What make is it? Maybe one of us has already tried it & can help.

[HareTodayDragonTomorrow]

It's this one from Lands End.

[BigGreenOlives]

There's only an inch difference in the two sizes. The sensible side of me says get the 12 as you can have the waist taken in but then I bet the 10 would fit on good days.

Bumping really for the after work/children have gone to bed crowd.