Just thought i'd mention this to anyone who hasn't seen it, Southern Rail (which covers the SDW) do a couple of E tickets which may be useful for anyone wanting to ride the SDW.
2 options, one covering all south stations and one for the whole network. Basically, gives unlimited access for the day (no good for overnighting unless you book 2 consecutive days):

http://www.southernrailwaytickets.com/t ... motionId=6

I used the "all network downloader" for £12.50 yesterday and got the train from East Croydon to Hassocks and then cycled the SDW (great fun btw!) to Eastbourne before getting the train back.