They look sort of thin to me. I have a Speckled Sussex from my local feed store (so from some hatchery) that is fatter. I have a couple Coronation Sussex and they dwarf my SS. I know they are the English style, but they look like a totally different breed.
It is difficult to see scale in the pictures. Click on additional photos and videos and you can see a video of their breeding stock. They usually have this on each breed page.