Have you brought dress www.hm.com/gb/product/04019?article=04019-A from H&M?
I really like the look of it, but I'm just not sure what the sizing is going to be like. I find that H&M dresses usually come up large, but it's a shirt dress, so I'm not sure.
I have massive norks, and have to be very careful of press studs. 
Not sure whether to get the 10 or not, the 8 wouldn't fit the norks, but the 12 might be too baggy everywhere else and look very frumpy.
My nearest store is quite far and it's also quite small, so they don't have a great range of things.