Hi to the OP... the UK is a real no brainer. A Vodafone simcard. I bought one on English Ebay and had it posted out here in early 2011 for a mid 2011 trip. That really wasn't necessary as you pretty well have to go into a UK Vodafone shop to get it activated. Mid 2011 I was using a Blackberry Pearl 3G 9105 or 9015, it wasn't that straightforward to get going but once going it was tops.
For GBP30 you have some options including international free minutes, 240 of them which allows you to call Aussie landlines (not mobiles) free of charge and most other destinations. As well as on the BB pickup your emails. I'm sure IPhones would work as well. We spent a week in Portugal with the same phone. Once there the calls are about 29p per min and don't work as well as in the UK. I used the international minutes very sparingly thinking this can't be right. But was able to run an international business phoning Australia, China, the USA and Italy while on the move. The same card should work in France and Italy but maybe with a surcharge like Portugal. If you run through 4 hours of free international mins, just buy another GBP30. Can't remember what the local UK calls were as I wasn't really getting the simcard for that.
Here's a link to the Vodafone UK where they talk of the "international" package and calls to overseas from the UK from 5p min. If you have look around their website (like every phone company it's like looking under rocks) you should get a good idea.
I found the Vodafone Wimbledon UK shop to be very helpful, the BB was a real dog to get going.
Calling Abroad – Make Cheaper Calls to Numbers Overseas – Vodafone
Fast forward to 2012 and just back from Rio with an IPhone 4S and still the Blackberry. The Blackberry spent the whole trip turned off in my luggage as it's pretty well useless. An Iphone with Skype you only need WI-FI to connect with the world. I had WIFI at most of my hotels and this worked. Did buy a Skype Aussie phone number for the IPhone while travelling which theoretically my family could have phoned me on from a normal landline. But if my home computer was on with Skype running chances are the computer would have "rang"
When travelling internationally I'm more interested in being the caller than the receiver.
Travelling with an Aussie simcard overseas is just a waste of money. Be it receiving calls, making them or data, the bill will be huge. Getting a local simcard or some sort of WIFI access is definitely the go!
Good luck with your trip!