Hello to all you guys raising money for Tommy's next year. I did last year's and found the £2k target quite daunting too but managed around £4k. I found everyone to be really generous particularly when they hear what you have been through. My wife and I lost our son Dylan in 2002 when he was stillborn the day after his due date. Our second son Oscar was there to cheer me, and everyone, on last year. :-)))
Good luck with the training. London is fantastic, take it easy, don't panic and.. do write your name on your vest. It makes a real difference as you'll never be short of support from everyone.
Tefal