Shocked this hasn't been posted already (if it has feel free to expire). Noticed this when looking at the Halo Reach deal posted earlier and as far as I can see it's the cheapest price online - it's around £38 at Game, HMV, Amazon, Play, Gameplay and Gamestation.
I've got way to much on my gaming plate at the moment to justify this, but thought this might do for some (and yes I know it's been cheaper previously).
Don't forget quidco and any zavvi vouchers that are hovering around at the moment, I haven't kept up with what's on offer there.
EDIT: casting my net further, it's at £29.86 with Shopto - some might consider them a better retailer...http://www.shopto.net/PS3/VIDEO%20GAMES/PS3LI03-LittleBigPlanet%202.html