Car rental/lease returns on national holidays

At airports, usually, yes. But you can always double-check for whatever airport and hire company you are choosing.
1st November is only a public holiday in some countries. In catholic Southern Europe yes, in protestant Northern Europe no.

Jim, have you reserved your lease yet? Are you planning to return it at Milano Malpensa, same as pick up? Why not do that and secure some details? Airport car rental offices typically want to know your flight arrival or departure time and tell you when they'll be closed. But my experience with the Peugeot buy-back program was that I made specific appointments to both pick up and return my particular car. They won't have a lot of cars in stock at Milan, since it's a French program and provides a brand new car to each customer: http://www.autoeurope.com/long-term-car-rental/fleet/

Laura, yes thanks. I have my voucher from AutoEurope and have paid for the lease. I realized that I had made my drop-off date on Nov 2, but that is when my flight leaves. So I need to change it to Nov 1 (holiday), this at MXP.