I started at about 9;15 - there's no set mass start time, though I think there is a limit to how late you start. Like I say, walkers need to start earlier, and provide a free guide along the first half of the trail. Obv, a little courtesy is required in passing groups of walkers.
There are a few points where you have to walk, and a number where it is sensible to walk to save wearing yourself out on a hill, so.don't worry about that.
I built up to 20-21 miles with a large hill early on for my last.couple of long training runs. On the day the lactic acid did bite at that stage, but you'll hang on!
If you van do a HM now, u should be.fine.to.build up.to it.
It was my first marathon , so its definitely doable - assuming you do at least some off road running though. First.half is hilly but very scenic, second half was a grind through muddy fields for me, very churned up and loads.of gates and stiles. However, I think that in someways this made it less punishing over all
It is informal and friendly, and generally well signposted. You can get lost though...I did! There's a map, but it is extremely detailed, and not really usable for runners. Also the terrain means it won't be fast.and the majority of people are walkers. If you don't start too early, they make useful signposts at least to halfway!
If you are building up to a marathon, have some off road experience,want a friendly less competitive environment, I'd say go for it....I recommend tea and Victoria sponge from the WI at the end.