Hi Karen,
Done this race a few times, it's a nice low key run, a little off road as well but not to bad, overall it's pretty flat.
You have plenty of time to train as it's not till august so slowly bud up your long run until 2-3 weeks before, then u should be up to distance. Maybe try some other races before hand, if you are Devon/ Cornwall based check out www.tamartrotters.couk for the race diary, they also have entry forms.
Have a listen to a free podcast called marathon talk, you can download it off iTunes, plenty of good running tips for all runners on there.
Good luck