Richard... there are easier ways to go, one is the A21, but am unsure how you would get to it. I suggest you come up M25 to A21 (Orpington turn off.Head towards Orpington) At next roundabout ( Hewitts ) take first exit. At next roundabout ( Badgers mount ) go straight ahead, and down Poll Hill. At the bottom of the hill is a turning on the left marked Otford. 300 yards to t junction(Pilgrims Way) turn left and drive straight into Otford. Avoid driving into duckpond,pub on left. Car park (large and free!) on same side of road, but 100 yards or so beforehand. Hope this helps.