I'd rather do Ditchling Beacon than Box Hill! Box Hill goes seems to go on for ever. And (as stated before) is part of a 15 mile detour, which is an additional 30% of journey we probably don't need to do.
That looks good, though I'd come down the closed road into Stamner village and not down Coldean Lane (and DEFINITELY not down the A27, that can't be right!).
The notes at the bottom are scaring me though. 2hrs 40 mins? Who's doing London to Brighton at 20mph average?! Bugger me!
Will set up JG page in next few days. Would be good to know timings - even if provisional - as I have work that evening.
Maybe suggest doing a dry run with car / foot prior to this? The Priestfield -> Amex one we did 2011 had a lot of major roads which were hairy in places and some serious...