We are planning a 10 night trip to London in a few months. What inexpensive SIM card plans should be considered for my unlocked Android phone?

I anticipate most use on wifi with Google voice (US number) and hangout dialer, but would like to be able to make restaurant reservations, receive confirmation calls or calls to and from the airline or hotel with a simpler connection. Calls back to the US would only be for something unexpected and I expect Google voice to be adequate for that. We might also want to make a call while on a day trip where wifi may not be available.

Besides cost, ease of purchase and activation is also a consideration.

Thanks for any help.

All the main providers, Vodafone, EE, O2, BT, 3 etc have cheap prepaid SIM deals. If you don't need coverage as soon as you land at the airport, just go into one of their shops and they will set up the SIM card for you. There are mobile phone shops on every high street and shopping mall, so you won't have to look long to find one.

Thanks, Heimdall. I checked the companies you listed. It seems that best inexpensive deal from each is 10 pounds, not bad. Then I saw that Vodafone has a neat plan for us. They give you a free SIM card, pay as you go, but the maximum per day is one pound unless you use far more data than I ever do. Since our trip is for 10 nights, it looks like this choice is a no brainer. Plus any use keeps the card valid for 6 months, saving the need for a new card when we travel to Europe again.