Cell Service

If you are going to be there for 3 mos why not just buy a local phone? My experience with wifi in Europe is not very spotty. Very similar to the US as to availability.

lexi,

Do you know if your iPhone 6 is unlocked? Verizon rep's should be able to tell you that.

If the phone is unlocked, the solution is very easy. Simply visit the nearest Carphone Warehouse when you arrive in London and buy a local PAYG SIM for one of the networks there. The sales staff can give you a good summary of the various options. That will provide you with a local phone number, which will also work other places in Europe. For a three month stay, that's absolutely the easiest solution.

Using your iPhone 6 will provide you with your familiar Apps, and will much more practical for a long stay.

What would a cellphone cost (just basic one) for Britain? Would I buy a certain number of minutes?

A basic Simfree (unlocked) can be had from £15, argos usually cheapest place , carphone warehouse not far behind.
Theres lots of companies and lots of monthly packages, but £10 should get you unlimited txt, 1 or2 Gb of data, and hundreds of mins call time.
As well as the Big 4 suppliers , have a look at Tesco and Giffgaff

I would steer clear of Giffgaff. I tried to sign on to their service and after a lot of back and forth emails, ultimately I couldn't buy minutes with a US credit card (the system said). Imagine my surprise when, a couple of days later, I was checking my account and found I had been charged anyway! Strangely, when I inquired about it, I never heard from them again. I disputed the charge and moved on.

If the poster's contract with Verizon is in the U.S., the firm's policy regarding postpay phones for an iPhone 6 ( which is 4G LTE): "We do not lock our 4G LTE devices, and no code is needed to program them for use with another carrier." For prepaid phones: "Once activated on our network, we do not lock our 4G LTE Prepaid devices, and no code is needed to program them for use with another carrier. To activate a prepaid device on our network, you must make your first monthly service payment."

I would use both your iPhone 6 and purchase a phone in London for use not only in the UK, but also for other countries in Europe that you will be visiting. Set the iPhone on WiFi; we have not had any problems using WiFi in the major cities. Use the local phone for calls and data in and around Europe. From the other posts on this thread you there definitely should be some phones and plans that will fit your needs.

Lexi - Like others have mentioned, I'd suggest getting a cheap paygo phone for the UK and download WhatsApp to make wifi calls back to the states.

lexi,

Based on the information that Bruce posted, it appears that your phone is unlocked. Therefore it would be very easy simply to buy a PAYG SIM card when you arrive in London, and continue using the phone and App's that you're familiar with. At the end of your trip, replace your Verizon SIM card and carry on as usual.

For three months you'll definitely want a UK SIM. It will roam all over Europe, and the rates are capped in EU countries. Do be careful to check the rates outside the EU - if you're going to, say, Switzerland, Norway, Croatia, or places outside of Europe like Morocco, rates can skyrocket. My friend has a UK SIM with great rates to the US and good rates in the UK and the EU. On my advice, he checked rates before going to Turkey - it was £1.50 per minute!

The only potential problem is that a UK SIM gives you a UK number. Your US contacts will have to be given this number so they can get you. Your US number won't be reachable when the Verizon SIM is not in the phone; see if you can forward it to the UK number, if you're expecting important calls on it. Or, learn how to check your Verizon voice mail from the UK, so you can do this periodically. Again, most UK plans have inexpensive calls to the US, so it won't cost much to check your Verizon voice mail, then call people back.

To add to Harold's comments, using a UK SIM is not really a huge problem. If any of your family or friends need to contact you urgently, they can make an international long distance call. For more routine conversations, just have them send a text to set up a convenient time when you're in a Wi-Fi area, and then use FaceTime / Viber / Google / Skype and have a long chat for free.