I was a size 26 a couple of years ago, not sure what I weighed as I never dared get on the scales but I would estimate about 22 or 23 stone. I got down to size 22 and about 20 and a bit stone. I'm now 17.11 and size 20.
I'm always amazed at how different people are in terms of weight and dress size, I know people in my LL group who are the same dress size as me but are much lighter. I suppose it just comes down to body shape in the end, where you carry your weight must make a difference to things like waist size. I'm a pear shape myself so I probably have a thinner waist than an apple shaped person of the same weight. However I carry lots of fat on my arms and calves and I can't ever wear anything that is tight is those areas (which pretty much knock out all non-stretchy tops!)