Did it a couple of years ago. Flew to Pisa(with Ryanair) hired a car and drove to Sienna. Stayed in hostel (cheap, cheerful, cheap). There was a classic car rally the week before with some fantastic mint Alfas and Fiats knocking about, some of which were used for suppport/style cars esp that Fiat 500 with the HUGE megaphone loudspeaker on the roof. 
Top event, even without a classic bike. Some of those old boys are proper HARD.
How you get there without Ryanair I dunno but my mate is doing it again (on a Rudge 3 speed) this year so if you fancy a 500 mile overnight drive after doing the Trans Provence drop me a line!