Buy SIM card in Amsterdam or London?

Dave, You could certainly buy SIM cards in Amsterdam, however when using them in London you'd be "roaming" and would have to dial a Netherlands number each time you wanted to call the other party. You could buy another set of SIM cards when you arrive in London, but it seems a bit of a "awkward" solution. Another option would be to purchase a SIM from one of the "travel phone" firms such as Roam Simple, Cellular Abroad, Call In Europe, Telestial or Mobal (there are others but can't remember them all). This would provide a European calling plan with consistent rates in both countries you'll be visiting. You wouldn't have to change SIM's or numbers when you arrive in London. These usually operate on a post-paid basis, with call charged to a credit card, so no need to "top up". With this option, you'd have a working phone as soon as you step off the plane, and wouldn't have to interrupt touring time to buy SIM's. Check their respective websites for details on the cost of SIM's and calling plans. Happy travels!

Thanks Ken, we'll probably just wait until we arrive in London to keep things simple. I may even buy a card on eBay before we leave.

Dave, I'd buy the SIM card over ebay if you can't wait until you get to London. I've had good luck buying top-up credit vouchers over ebay, but the first time I did so I had to log on to the U.K. version of ebay to do it. After that, I just went to regular ebay and clicked on past purchases to buy another voucher. My U.S. ebay user name and password worked fine on the U.K. version. The one drawback will be finding a seller that will mail the SIM to the U.S. Don't pay much for the SIM because they almost give them away in the U.K. and the initial credit on it won't be much. Be sure you can buy a top-up voucher over ebay for whatever carrier you find. The travel phone firms mostly use a U.K. cell phone number for the numbers they provide so buying a U.K. number directly saves a bit of money. Rates for roaming are all capped by the E.U. so they don't really vary much. I have had experience with T-Mobile U.K. and successfully used phone numbers from them in Germany, Italy, and France this summer. As soon as you get to a new country, you get a text message in English advising you of the cost of calls. You also get a text message telling you about roaming data packages you can purchase and how much they cost. The data packages were the best deal because every other type of phone data service costs a fortune. It is very possible that you can buy SIMs in Amsterdam that will work fine in the U.K. and it is possible that the cell companies in the Netherlands will offer comparable packages. You should be able to find out online or when you get there if you can wait.

Thanks for the info.

One additional thought. Because you don't plan to call the U.S. with you cell phones but just want them to communicate with each other, can you just use a U.S. carrier and communicate by text message? If you have T-Mobile or AT&T as your carrier, text messages aren't super expensive (but aren't free, either). It would save you the trouble of finding and configuring a U.K. or Netherlands carrier. To avoid getting calls from people from home who don't know you are out of the country, you can unconditionally forward all your incoming calls to voicemail. On our trip this summer, we used our T-Mobile phones to check in with each other by text. Because we have unlimited message plans at home, incoming texts were free. Only the sender had to pay the international rate.