Asda Middlebrook (Bolton, Lancashire) are selling 256Mb Creative Zen Nano Plus for around £25. Only downside I see is the lack of space with it being a 256Mb MP3 player. Not a bad offer for kids or someone who only listens to a few songs. It also has a voice recorder and FM radio.
You will find them on a shelf in front of the till in the CD & DVD section in the store (this is on your left as you come through the main entrance)