Eastbourne is only a 2 hour drive from London or a similar length train journey!
Our first section was from Eastbourne -> Southease. It is possible to park in Eastbourne then walk from Southease to Lewes (~4-5km) on the way back (the Information office in Eastbourne didn't know how to get back). There are also trains from Southease to Eastbourne (every hour). There are more frequent trains from Lewes to Eastbourne (£6.70 return) and the walk from Southease to Lewes is very pleasant running along side the river.
In case there was any doubt :) :