I live in "Europe" (France to be exact) and wifi is extremely easy to find if you live here. Two of the three biggest ISPs here turn every customer's wireless router into an access point to share with other customers. The result is free Wifi within 500 meters of almost any residence in the country.

In addition, two of the three carriers offer unlimited Free wifi to these access points with the iPhone plan, even if you're not an ISP customer. So you're doubly covered.

I checked the iPhone plans of the UK and Germany, and they both offer free Wi-fi access with the iPhone plans.

Regarding your other point, I think it was clear from the UI of the phone call that a voice chat icon will appear when video chat is available and you can switch to it at any point.