I'm just 5" and around a size 16-18 at 14st 4lbs.
I've very hourglass shaped and my chest is 34G. In Next, I wear a size 16 jeans from the petite section, same in Dorothy Perkins. I know in other shops, I would only fit a size 18.
Top wise, depending on the top, I usually wear 14-16. Dresses size 16 unless they have stretch to them. Clothing with no stretch in it has to be a size 18 to go near my arms.