Re entry: this year (Sept 2012 for 2013 entry) they staggered the applications so for instance if you were 20 mins + inside the BQ for your age grade you were allowed to register on the first day; then 15 mins to 20 mins on 2nd day etc etc.
So it actually filled in about two weeks but in a controlled manner with the fastest qualifiers (by gender age band, not absolute times) given first shot then the charity hordes at the end, but only about 6,000 of them.....
They also give you a chance to log an improved run if you have a faster time after the original BQ. In my case I BQ'd at VLM 2012 but improved in October 2012 so submitted my better time by email. I now have two acceptances......., but obviously only one place.