Me too...I live just outside Brighton so am always happy to help with that end of the course. Devils Dyke, Saddlescombe, Ditchling Beacon etc.
My max to date is 100k so this is one step beyond for me
If anyone is free next Sunday, there is the Jog Shop 20 'race' which although doesn't take you over very much of the SDW it is in the area and gives you a feel for the terrain and 'undulations'