I am taking the plunge and travelling to the UK with my Samsung Galaxy S4 smartphone. I will not be calling back to the States (using Google Hangout to video chat instead). I wish to phone, text, and use my apps for things like restaurant reservations, checking transport schedules and navigation while sightseeing and touring. Bringing along a wifi tablet to use in our hotel room. All my phone/data useage will be in-country during our 11 day stay.
Any suggestions on where to go for getting a SIM card for my unlocked phone? Prefer to buy face-to-face at a counter. Buying from knowledgable customer service staff is always appreciated.