The Ordnance Survey Explorer Series is the most useful if you would like to visit countryside sites and use local paths. As the High Weald is a large area it is covered by several maps.
Explorer Series, scale 1:25,000, 2 1/2 inches to 1 mile (4cm to 1km )
123 South Downs Way
124 Hastings and Bexhill
125 Romney Marsh
134 Crawley and Horsham
135 Ashdown Forest
136 The Weald
147 Sevenoaks and Tonbridge
The Ordnance Survey Landranger Series may be useful if you are less interested in detail.
Landranger Series, scale 1:50,000, 1 1/4 inch to 1 mile (2cm to 1 km)
187 Dorking, Reigate and Crawley
188 Maidstone and the Weald of Kent
189 Ashford and Romney Marsh
198 Brighton and the Downs
199 Eastbourne, Hastings