The problem with Medion laptops is that if something does go wrong, such as a CPU failure, the repair will cost a lot more than other makes and can even involve it being sent back to Germany..
The Packard Bell one from Currys looks good but look around for other deals such as this one
http://www.technoworld.com/productdisplay.asp? ProductID=41672
Whatever you decide, make sure that it has at least 512mb of RAM as all laptops at the lower end of the market have shared graphics which require a portion of this.
256mb will not leave enough spare to cope with XP adequately.