Rich I don't know any of the course other than what I've been able to look at via map but so far have only known the course route first time for one of my races. So plan is for me to turn up the day before, find the start and then wing it on the actual day.
I emailed the organisers with a few questions who were helpful enough to send me details and a lovely marked out route map which made my life much easier.
The 50k starts at 9am and then the marathon at 9 and so on and so on. The way the route goes some of the marathon runners may bump into the fast 50kers soon after the start but thats all.
At least the dog is out there with him and not just stuck indoors getting fatter. I've seen an old woman on a mobility scooter with her dog going over the south downs before which is true commitment to walking your dog.