Prepaid SIM/SIMs for Italy, France and Switzerland

[Wanderer]

Hello,

I'm travelling to Italy, France and Switzerland in about three weeks. While I'll have international roaming on my Australian 3G/GSM service, I want to get a SIM for local calls and SMS - incoming and outgoing. I have no need for data services.

My first port of call will be Rome Fiumicino Airport, and thereafter Firenze for a few days - I'll be bypassing central Rome.

Should I aim to get a single SIM to cover my entire trip, or get a new SIM when I get to France (initially in Nice)? (I'm only in Switzerland for a few days, so won't bother there).

Any suggestions on the most appropriate SIM provider(s) would be appreciated. English instructions for recharging would be an advantage as I know virtually no Italian, but I do have a moderate understanding of French.

Thanks,

Daniel