My wife and I are traveling to London and Liverpool next month. We both have unlocked iPhones and will be buying SIMS at Carphone Warehouse when we get there. Luckily one of their stores is just one block from our hotel. I was just on the Carphone Warehouse website looking at options and got horribly confused with stuff about tarrif, etc. All my wife and I need to do is have the ability to call each other, text each other and use the internet (when not on wifi). We'll be there a total of 7 days. Can someone help me with what to look for in terms of purchasing SIMS, on which carrier and will we also be able to get calls and text from family back in the U.S.? Also, is it possible to buy a data-only SIM for my iPad Air? I really appreciate any and all advice/guidance.