So, i'm going to NYC for a few days in january, and since i want to be able to stay online on my phone while i'm there i'm looking for a good and easy deal on a prepaid simcard.

My previous visit to the US a couple of years ago taught me that the mobile market over there is a bit weird, and they don't exactly like to accomodate tourists and other prepaid users with data on their iPhones.

I've noticed that Three UK is offering free usage of data allowance in the us, and their prepaid plans are a rather good deal, so i'm thinking that this is the way to go.

Is there anywhere in Heathrow T5 i can pick this up? I have a 2.5hrs transit there, and can go both landside and airside.

I should note that i need a nano sim

If this solution sucks, i'm open for other suggestions