Nokia 1661 on Virgin Mobile at Morrisons for £12.50; found at the Cambourne shop near Cambridge. They had almost none left but said they were expecting more.
This is a pretty good price for a not-quite-basic phone (colour display, torch, loudspeaker, radio), I bought one to get a spare battery and charger, I didn't need the phone at all!!#
sorry about rotated image, flickr doesn't want to play nicely for me :-(