A few days ago I posted my work in progress here, so let me show you the finished frock!
I used a children's pattern as I couldn't find a shape I liked. I wear a UK 8/10 and cut an age 14, and it was very roomy as you can see.
The pattern I chose was New Look 6171, view A. I think it would fit anyone up to a size UK 12. Its great for work as I can throw it on in the wee hours of the morning and not have to fuss with zips, buttons etc.
Will use this pattern again, look out for updates :)