Hi Charlotte,
I think its great that you're fundraising for the CF Trust - thank you!
Am I correct in assuming that you do not have CF? (If you do, I am all the more impressed - way to go!)
If you don't have CF, I think your fundraising would go better if you had a CFer to "run for." Do you kow someone with CF who wouldn't mind "sponsoring" your effort?
If you can attach a face to your fundraising, you will do much better (especially if its a young child - don't be afraid to tug on those heart strings!!) Then on your website you can write something about your child such as:
"I'm running the london marathon for "insert name here". "Insert name here" is a smart, delightful seven year old, who has inspired me to train for a run in this difficult event. "Name" is living with Cystic Fibrosis. CF is a genetic disease, etc etc (insert generic definition of CF here... look at CFF.org, etc. for a brief one). Please join me in my effort to raise money for CF research by donating to my goal of (insert sum).
Thank you for your support.
Hope this helps!!
Chris
25 w. CF