In reply to Luke90:
Yep, if you live in Sheffield or Chesterfield, or thereabouts, grit is slightly closer than limestone, I guess it's true for Manchester, Leeds, Birmingham and the cities and towns around them also - that's quite a chunk of the UK population.
Grit gets soloed a lot too, on a nice summer evening at Stanage you'll see lots of competent folk out soloing route after route. I can't think of many limestone crags where you can do that. On my birthday a couple of years ago I soloed 45 mini routes, none much harder than severe, and it only took me a couple of hours. Even banging out the 4s and 5s at Horseshoe I couldn't get close to that many in a similar time (I don't think there are that many easy routes either!).
And then, of course, there is lots of talk and coverage of grit, so new climbers or non-locals all want to come and have a go too. A bit like Ben Nevis or the Northern Corries taking a huge chunk of Scottish traffic.