Not got round to it... And probably never will...!! :oops:
However I know a few people who have and getting a place is very difficult, especially on the 1st year of application. Getting one through a charity is one way (quite a number of charities arrange a block of entries, and you need to prove that you can raise them plenty of sponsorship), another is to have gone on other runs & 1/2 marathons, etc, to prove that you're serious.
Good luck!