Take the S 65 From Bologna south. This is, I believe, one of Ducati's test routes and if you ride it you'll understand why their bikes handle so well. There are plenty of interesting side roads to investigate as well.
From Lass O'Richmond Hill car park to Brighton beach, only a roads and B roads. Once past Chessington some nice scenery and twisty country roads with mainly small villages. Cutting down the side of Gatwick airport is slightly more urban but quickly breaks back into country roads with just Haywards Heath as a mid size town which is largely bypassed. approx 2hr 15- 2hr 30 minutes ride time. Nice involving ride for older machines or anyone not in a huge hurry!