Thanks, everyone, that's a pretty impressive list of names...and I don't see why Michael Vaughan shouldn't 'count'.
I had forgotten about the two famous boxers (and not heard of Kell Brooks), didn't know about Vardy's background or about Coe's Sheffield links. There are some HUGE names here, across a wide variety of sports. Anything from rugby, league or union? Or snooker, apart from the famous venue? Swimming?
Okay, I've cheated. Here's a list from Wikipedia (Sheffield-born in bold type):
It includes a cricketer I had never heard of - a guy who played a couple of games for Oxfordshire! Nobody from swimming or rugby, but there is a surprising number of football managers, as well as one of the great goalkeepers. 'As safe as Banks of England,' they used to say.
Also, Yorkshire cricket legend George Ulyett, who appeared in the first ever Test Match, and also played in goal for Sheffield Wednesday, I now learn.