I've never heard of it sorry!!
My mates go to something similair in Stoke so I'll ask them who runs them. I don't think they are restricted to just big people though because I remeber seeing an advert saying something about BBW's and their admirers.
It just struck me when chatting to my niece yesterday that it would be nice for her to be able to be amongst like minded non judgemental people which I know Biggies are, which is why I posted the link.