I've reached that age where I need to run a marathon!
I've done a couple of halves and it's time to push myself again. I have some strict criteria though 
I only run off-road and it needs to be in the 2nd half of the year (so that I can train in the lighter evenings) preferably in the U.K., and whilst I train on the South Downs I don't want too hilly.
Recommendations please 