I've travelled to Greece quite a few times for work and pleasure,and Italy many times.The quickest and most expensive route to Italy from Calais is via the French autoroutes(Pearge) and through MontBlanc tunnel to Aosta,Iusually go across Belguim free autoroutes via Lille,Mons,Namur down E25 to Luxembourg,Basle through Switzelland and on to Milan,40euro Swiss road tax(12mths) and some tolls,but offset by very cheap deisol in Luxembourg.Italian autopista tolls a bit pricy,I usually use SS roads which are free but not so quick,for Bari West coast or East coast routes from Milan much the same distance,also another Greek ferry service from Ancona further North.Another option is Calais.Lieage,Stutgart,Munich,Innsbruck,Brenner Pass,Trento and onwards South,German autobahns all free travel vignette for Austria around 20euro and toll for Brenner about 15euro and a really beautilfull drive either way,I usually go down one and return the other.Stops/campsites depend on how many miles you like to drive daily,Switzerland,Germany,Austrian motorway services safe and free for overnight stop,many with service points,French,Italian areas less safe,but still plenty of service points.Prices assume your van is under 3500kg.Which ever route you decide on its through some lovely countries and Greece is glorious,hope this helps enjoy your trip,Paul