If it's any clue, the chap on the plot next door, who's a very seasoned gardener as asked for "some of them plants" if I've got any spare this year - yes I'll be growing them again, they do have a long growing season though, cut the last one about 2 weeks ago. It was about 7" across - not huge you may think - but believe me for our soil it is!
Over winter seems to be the only way we can grow caulis on our site with the club root problem, but I've got a load of allegedly club root resistant plants in this year, (Clapton), so we'll see how they do.