These are really soft and comfy knickers. I would say don’t size up. I’m a 12 and usually buy 14 in knickers so that you don’t get any flabby bits where the tight elastic is. I like a streamlined look. These are loose and just skim and stretch a lot and I really like them. I did buy a 14 to try and they are slightly loose so the 12 is better. Don’t worry I’m not returning the 14!