East Sussex combines the South Downs with Ashdown Forest and a good stretch of coast, giving a real variety of riding country within a single county — chalk downland, forest tracks and coastal hacking are all genuinely available depending where you are based. Hunting and Pony Club culture are well established, particularly around the Downs.
Some of the best riding country sits on common land or National Trust and Forest land with its own access rules, so it is worth checking what bridleway access actually looks like near where you would keep a pony rather than assuming open countryside means open riding. Prices follow the wider south-east pattern — expect to pay for grazing and livery, with the coastal towns and anything close to Ashdown Forest carrying a premium.