My new position has me traveling between the UK and US very frequently, and I have been researching getting a UK SIM card to use in my phone, instead of using a crappy work-assigned phone, or spending a ridiculous amount of money by roaming with Verizon. It looks like a SIM from Three will work mostly fine in my A1533 iPhone 5S (as the only unsupported LTE band is band 7, 2.6 GHz).

Does anyone have more specific experience with this? Is this something that other people would find useful if not?

Welcome to FlyerTalk.

You should find these threads helpful:

http://www.flyertalk.com/forum/trave...and-wales.html

http://www.flyertalk.com/forum/trave...merica-uk.html

If you are regularly in the UK and dealing with UK people who will want to call you on a UK number, you should consider getting a regular contract with Three. The normal contract includes Feel at Home which counts all calls received in the USA on that SIM, and all calls to the UK on that SIM whilst in the USA as included minutes. This effectively gives you a UK number to receive calls foc for your contacts to use, as well as an ability to make free calls to the UK foc - particularly valuable to mobile numbers which would otherwise be very expensive.

My Colombian iPhone 5 works fine on Three. It is an "Americas" model so probably the same as a USA iPhone 5

I do not spend enough time in the UK to take advantage of the suggestion made above by lhrsfo so just use the 321 prepaid plan. Last time I accidentally bought a �15 all you can eat add-on which didn't prove particularly good value for money. �15 was much more than I would have otherwise used on the 321 plan.

Complicating things, USA geographic numbers are actually included in my plan, so I travel with 2 iPhones. My home iPhone I divert to a New York DID which in turn diverts to my Callcentric account which forwards to my other iPhone with a Three SIM in it. I get free text messages and data roaming on the home iPhone so I have all bases covered and forwarding the inbound calls from one phone to another is much more economical than voice roaming.

When I was in the UK over the summer, I used my A1533 iPhone 5S on 3 UK. No issue. I believe it's the only carrier in the UK for which the VZW 5S has all LTE bands. You even get the "HD" voice on 3 on the 5S. Also, instead of LTE, you'll see 4G on your phone as an indicator.

The fastest I got on 3 UK was ~25mbit(At the Doctor Who experience in Cardiff(hey, had to upload my photos to dropbox somehow!)).

This was actually my plan; I'll be spending about half of each month in the UK and had heard good things about Three. Is there any difference between a recurring monthly contract and going the top-up route? I'm not 100% clear based on the site info.

Perfect; that's the model I have and the carrier I intend on using. You are a godsend.

Unrelated: sucks about the Isles moving to Brooklyn next season, especially with that godawful seating setup on the one end. I hope they win the cup this year, go out of Nassau with a bang