I posted somewhere in another thread, but when I was in the UK last (May-June), I picked up an O2 sim card for my old iPhone 3 for GBP 10, and it was good for nearly unlimited data/text, and I used it for a couple of UK calls. The entire purchase process took no more than 5 minutes, and that included them helping to change out the sim card.

We went out to the Stratford Mall (near the Olympic Park), and there's shops for nearly every UK provider...many of them either beside each other or just across from each other.


We also went to Germany on this trip, and it is a bit more challenging there. I did get an O2 sim card, but I think it was E30, had to provide a passport, address (the clerk just used his), and in general it took about 30 min to do it all. The odd thing was, the first O2 store I went in they just said they were out of sim cards and come back tomorrow. I kept walking, was about to go into an Orange shop, when there was another O2 shop, where they had one.