I got a "personal" email I once expressed an interest and was actually told I could have a place for 2012 - I think they must just lurk on various forums looking for people who are a little bit unhinged when it comes to running challenges!!!
Birdy - I gave up my club place for London this year - it ended up with just my name and two others who hadn't done it before in the hat and as there is only two places felt I should let someone who hasn't done it before have the experience. The thoroughly enjoyed it and I wasn't fit enough anyway so worked out for the best, will not be giving up any places for next year though.
Right off to lurk on sub 4.30 again.