Hello, I've seen some nice tops and a gorgeous leather jacket in Massimo Dutti. I'm usually a size 12 (very occasionally a 14), petite framed but huge Norks and a bit of a mum tum. I was going to order a 12 when I noticed on the website that it says that the very tiny models are wearing a size 12. Do the sizes come up very small? Do I need to go up one or even Two sizes?