Head to Southese station. From here you can walk along the River Ouse straight onto the sublimely tranquil South Downs landscapes. You will walk through the village of Rodmell village, past Monks House, owned by the National Trust, and originally home to Virginia and Leonard Woolf. Shortly after this, you will climb up onto the Downs (which always seems like an odd thing to say) and follow the South Downs Way, the main hiking and cycling artery of the South Downs National Park, through fecund farmland with spectacular views, back in a large loop to Southease.
There is a Youth Hostel just beside Southease station with an all-day café. Or stay the night, and take on another day trip hiking from Glynde, easily accessible from Southease station, as well.
Total distance: 8.8kms
For more details on both the Southese and Glynde looped walks, see the South Downs National Park leaflet, but always bring an OS map too when possible.