Hi John,
We have made three trips to Italy over the years and the route we found to be one we enjoyed most(from a cost/scenery and traffic viewpoint) was from Calais to Lille, Luxembourg, Karlsruhe, Baden Baden,Basel, Lucerne, Lugano, Milan, Genoa, Pisa. This was about 1000m I think but you can check on Michelin or Google. Autostradas in Italy charge as do Swiss autoroutes. Mont Blanc tunnel also charges of course and you will require a vignette for Swiss autoroutes. German, Belgian and Luxembourg routes are free. We have never stopped overnight at any service stations and whilst there is no law to stop you from doing so, most caravan folk will recommend you do not. There are more than enough campgrounds within a short distance from that route and you will certainly get a better night's rest there than parked in amongst the trucks at service stations. Apart from the fact that stopping overnight at campgrounds en route is a pleasurable part of the caravaning experience itself you will also avoid possible break-in's or muggings which some friends of ours experienced in Italy last year.