JJ & Red, I've not yet been able to find out the Bournemouth marathon route - there isn't anything on their website yet, and one of the FAQs says "all road closures and consequently the route will be signed off at the end of january and will be available to view on the event information pages from this time." Parts of Bournemouth are quite undulating, but they may have a route along the promenade for quite a bit of it, which would be flat.
Haven't taken all the decorations down here - stage approach. Those emotions still well up don't they Red, even as time passes - sometimes out of the blue, but those nice comments would certainly do it.
TE, I have done the New Forest half, but not the full marathon. Each time I've done it, it has been very warm! I don't like the fact that the road parts aren't closed to traffic, and some drivers are very inconsiderate, but as you say, it is picturesque.
I'm not sure I went as far as 20 miles when training for my first marathon, though I intended to. I didn't have very reliable measuring tools then! Thre is a useful 20 mile race in March quite locally, so that has been a useful one for the Spring marathon. Nothing much on offer over the summer for an autumn marathon preparation.