I'm doing Hellrunner in November this year.
PUMA HellRunner Homepage
I think there are still some places left. The marathon will be a breeze after that!
I'm trying to get a place for the Marathon next year too in aid of the Prostate Cancer Charity. I'm entering as many 10k's and half marathons in the mean time.
The Great North Run is always a good one too.
Good luck trying to get a place!