Right - starting at 8am isn't too bad a time, but a bit of defensive routeplanning won't go amiss. I don't know where you're starting in London, but, assuming it's not wildly to the east or the west I'd go through Clapham, Tooting Broadway, Mitcham, Wallington, turn right just before Coulsdon, go up the hill to Chipstead, on to the junction of the A217/M25, take the A217 downhill to Reigate, go round the one way system following the signs for A217 south, go over Cockshott Hill, cross the A2044, turn left on Lonesome Lane, go straight on through Meath (by which time the teddy bears will have caught your notice), keep straight on through Horley town centre, passing Waitrose on your left and the station on your right, join the B2036, go south to Cuckfield, take the left turn signposted Haywards Heath, turn left on to the A272 and go downhill in to Haywards Heath, go round the one way system (not great), go south on the B2112, turn left for Wivelsfield, follow the signs for Lewes, join the A26, as you go in to Lewes avoid the left turn that goes downhill for the town centre, follow the signs for Rodmell, and, once you're on the Rodmell Piddinghoe road, go in to Newhaven over the bridge and turn right for the ferry port, which is well signposted.........