Interesting, Yorkie...
I was in Tesco this morning, and saw their sim cards stuck around the till for varying prices!
I suppose you can buy one for - whatever, and use it until the money runs out, then buy another one!
I'm sure chums here know how they work, but as of yesterday, my old Samsung Fiddly-Fat-Finger Thing still seems to do something or other, I'm not sure as I don't tweetett, or use bookface......
...well, in a way...