Short Term Mobile Phone Rental?

[Earlybird]

I've got a friend arriving from America in a few weeks. Anyone know if/how/where I can arrange for her to rent a mobile phone for the duration of her 3 week stay? Is it eye-wateringly expensive? She'll be arriving at Gatwick....if that makes a difference. Would appreciate any suggestions.

Do you have any friends who have an old pay as you go sim card and phone? I think we may have one tucked away somewhere - I can certainly check tonight - then all you would have to do is top up the phone and she could use it.
I'll check if you want me to?

Or barring that, it would probably be cheaper to buy a pay as you go than rent one. Are you sure she doesn't have a tri-band phone already? A lot of the newer ones are. If she does you can get it unblocked cheaply and easily and then just use a pay as you go sim card in it.

The post office in kings cross used to rent them by the day or the week, not sure if it still does as I haven't been that way for a while. Prob not very helpful!!