If you go depart from southhampton the NORTORIOUS Bay of Biscay is as unpredictable as ever. Generally the Med is calm, but can have some rough seas occassionally.
You can, as here, get some glorious days in November in the Adriatic but you can get cold weather, storms and overcast weather as well. Venice does get very cold occasionally so be prepared for all sorts of conditions. I don't think you will need your bikini on deck too often.... Neil.