Crash Hamster, I was reading your post thinking 'that sounds okay' until I got to your 18 and 19 mile bit - that has scared me just a little!
Tom - I've just done a half and have entered, think you should go for it. The reason I was thinking about this one over a flatter one is that I might not get so preoccupied with my time and just concertrate on finishing!
I think if I entered a flat one, even as my first I would keep looking at my watch and I've been told that that's not a good idea for your first attempt at 26.2 miles?
I've got a bad hip at the moment and so haven't run in a fortnight, I'm hoping I'll be able to ease back into it next week... fingers crossed....