Where to buy?

[geoff]

I haven't been to Europe in years, and will be meeting my wife in London after her business trip at the end of the week for a week in Scotland. I'm flying into Heathrow and meeting her at a train station. I'm sure my old German T-Mobile prepaid sim is long dead, and my US CDMA Verizon phone doesn't do international GSM frequencies. My options are to switch US phones or carriers before I leave, or pick up a UK SIM as soon as I land. If I understand correctly, there are SIM vending machines (Vendpoint?) around LHR. Is this my best option? I want to be able to call my wife after I land so we can coordinate on meeting up for the train ride to Edinburgh