As BCM mentioned - he might sort a ride in the area.
I'm not local - Amberley is two hours drive for me.
Presumably, most of you locals have ridden out on bits of the SDW quite a bit?
I'd settle for a ride that just went out and back along the SDW, a recce ride so to speak - 20 miles out - 20 miles back
Take in a couple of bigger hills
It would give people a chance to assess whether this is the ride for them before they commit and find it isn't.
Fine, if you can pick a train station that works for you, its not a problem. Possibly something like Amberley and go to Brighton and back or just do Brighton to Eastbourne, there are a few places. Earlier part of the ride (Winchester to Amberley) there aren't many stations nearby.
Winchester to Chichester is about 35 miles offroad, but then 10 miles on road to get to CHI, so not sure if that works for you.
Ultimately the run entails doing quite a few 100m to 200m climbs, with the odd river crossing that sees you near sea level. none of them are that gradual but they are fairly even, if a bit steep.
over the whole run, I think Brighton to Eastbourne is possible the nicest section, and there are a few more villages that end, the first bit is a little sparse but none the less, its a good run and I don't think you would begrudge any of it.
excepting the hill out of Amberley, which is steep as ****
(edited for typo's)