Advice on how best to communicate for 12 days in UK, including which Verizon package. Also, better to rent GPS unit or use app on phone? Or purchase phone and minutes upon arrival. Current phone is 4s, equipped with int'l Sim card.
Take your own GPS with Europe maps (or buy one there). You already know how to work it and can program in some destinations in advance. It will be much cheaper than renting one for 12 days. If your map app uses data, the cost will eat you alive if you use it constantly. How much calling do you intend to do? I have made four trips to Ireland with no phone at all, and only needed to make a couple of calls on one of them. What kind of international SIM do you already have? I don't know what options you have with Verizon, so I can't comment on that. A bit more info about your needs/options would help us advise you better.