Asos dress size advice

I love this dress in black but i'm size 10 and there are none left, was thinking of ordering the 12 instead. Does anyone know what the sizes at asos r like, as I know sizes vary depening on the store. Judging by the size guide chart size 10 looks more more my size the waist/bum area might be a tiny bit big on size 12 but then again maybe it's stretchy.

Out of the blue or green colour which is nicer? They both have size 10's left. Any eperience with asos sizes would be great thanks!

http://www.asos.com/Asos/Asos-Twist-Middle-Body-Con-Dress/Prod/pgeproduct.aspx?iid=1393302