Link for PC World http://www.pcworld.co.uk/gbuk/sony-lego-harry-potter-years-1-4-06774014-pdt.html
Become part of the magic and play LEGO Harry Potter: Years 1-4 for the Sony PSP, the perfect game for Harry Potter and Lego Game lovers' everywhere.
Based on the first four Harry Potter books and films, this game - now on the Sony PSP - takes you through potion-making, spell-casting, puzzle-solving and lots more magic that will make the Harry Potter stories come alive. Players go from Privet Drive all the way to the Triwizard Tournament in an interactive journey and discover a whole new dimension to Harry Potter, his friends and his magic!
Next cheapest seems to be Amazon at £10.98
Seems to be limited stock but I did find some in both Currys and PC World near to me.