Just a thought, but there is a variation on the skype idea; if you have a mobile phone contract with the three network -
www.three.co.uk then with some of their phones you can make and receive free skype calls wherever you are because the skype service is actually working over their mobile phone network. I'm not sure how they do this for free but it is available and on pay as you go and pay monthly contracts. Seems like a great deal.