My brother is coming over from the US for a few weeks and wanted a mobile. I was going to put a PAYG on an old phone I had but then saw this in store:
http://www.carphonewarehouse.com/mobiles/mobile-phones/ALCATEL-OT-206/PPAY
for the princely sum of Ã,£12.95 it's a new phone (albeit placky and garish) but with Ã,£10 airtime on O2.
If anyone is looking for a very basic phone as a backup / for the car etc then you could do worse.
It seems to work fine but hey, for a few quid, don't expect to be able to browse the forum.
It's incredibly cheap. I'd rather pay a little more for a more usable phone, but we're back into the days of throwaway phones.