1. I did a Euro rental recently and they converted the charge from Euros into GBP and charged me in GBP. The irritating thing is that they add a rip off 4% commission for the privilege. Insist that they charge you in Euros and let your credit card company do the conversion for you (they will charge less commission).

2. There used to be restrictions/extra insurance if you take a car to Italy (when you see how they drive, you will understand) but I can't recall having any problems last time I rented there. Certain cars top end cars (Porsche, Merc and BMW) probably do still have restrictions, so check in advance if you want one of these.

Third party insurance is a legal requirement in Europe and I think you will find that it is included in the price and can't be declined, regardless of what cover you have. You can probably use your card to cover the additional insurances.

3. Could be airport fee, car registration fee, sales tax... They always seem to invent a bunch of hidden charges to lump on to the poor renter.

4. Int'l Drivers Permit? You will probably be OK, but the best thing to do is ask Avis or your local motoring organisation (who will doubtless try and sell you an international driving permit!).