Whiterabbit: I wouldn't say t-mobile UK dongles will be cheap but it does seem the cheapest option relatively when on the move.

50mb for £10, approx $15 allowed over 30 days is not too bad, particularly the 30 day limit. Or for £5, 20mb for 7 days.

It's really going to make my holiday in France more enjoyable as I won't have to worry about finding and topping up sim cards when arriving. And I hope T-mobile will continue this offer.

What offer is this? My wife and I will be arriving in the UK before going to France. Are we better off getting a T-Mobile UK SIM and using that in France?

Newbie here... If I bring an unlocked iphone with me to France, wouldn't I buy a SIM in France for voice and use wifi for data? Will that only cover web browsing? Is text messaging considered data or voice? I am so confused by all of this...

Messaging is messaging, data is data, they are 2 totally different things. There are BTW also websites which offer to send SMS.