OK I think I have it at 403.5km
HallChiddingstone Causeway TQ 51783 46560
Golden Green TQ 63612 48260
Hall Peasemarsh TQ 88428 23020
Battle TQ 70801 12354
24hr Garage Lewes TQ 42004 10539
Westmeston TQ 33839 13629
Outwood Green TQ 32685 45490
Hall Chiddingstone Causeway TQ 51783 46560 end lap 1 197.3km
Loose TQ 75566 50810
Hall Sittingbourne TQ 91128 63461
Hillborough TR 21110 68032
Aylesham TR 21800 50231
near Lympne TR12733 36201
Hall Bethersden TQ 92923 40270
Finish Hall Chiddingstone Causeway TQ 51783 46560 Lap two 206.2km
Total 403.5km
My only concern is the distance between Sittingbourne and Bethersden and some faster riders will be in the night it could do with a 24hr garage for a feed stop or they carry bonk rations