This is a hugely challenging marathon with some of the best varied and technical terrain I've ever had the pleasure of falling over on. I ran this a while back as a warm up for a spring Ultra and it was absolutely fantastic. I'm gutted I'm not able to do it again this year.
Are you still providing the free swim after with that excellent breakfast?
I've tried Worthing Striders out before and they're a very friendly club who basically just seem to enjoy running and doing it together. Alan Rich is the coach there - he seems very dedicated and if you have a specific goal in mind he and the club are happy to support you in that. The Harriers seem a bit more track-focused and in fact when I did try and contact them about longer-distance training a while back, I didn't get any response - I could have tried again, but read into that what you will.