I just went to take a dress back to swop and I tried this (and practically everything else in the shop on) in a 14. I have a generous pair of boobs and it looked gorgeous.
www.johnlewis.com/210132/Style.aspx?source=63258
It looks really plain but in reality its lovely and floaty, its a very flattering shade of blue, not quite navy.
In the end, I never got it, I decided to keep the one I was taking back!! I wouldve lost my discount otherwise and I already have a similar coloured dress. I would recommend it if you arent a skinny minny though.