There will be loads of people of different abilities I am sure. Shame the link is broken for the results for 2011 on their website. Bet it'll be a great event - definitely one I am considering.
I do silly times too - very dark and miserable and cold and I use all sorts of delaying tactics but eventually get myself out and by the time I get back I have persuaded myself that it was a really good thing to do and I can live with being office-bound for the rest of the day! Have started at a club so that some of my runs are now in the evening so that I can fit in more sleep but somehow this makes those days when I get up early even harder. Nevertheless being in a club is really great.