I was just looking at the Lego Star Wars deal for the 360, then went further into ChoicesUK stock lines to find games I didn't have.
I found the following that were either the cheapest or cheaper than on http://find-games.co.uk
£17.99 Lego Star Wars II - The Original Trilogy (Xbox360)
£17.99 Eragon (Xbox360)
£14.99 Far Cry Instincts Predator (Xbox360)
£17.99 Godfather, The (Xbox360)
£14.99 Hitman 3 - Blood Money (Xbox360)
£14.99 Moto GP 2006 (Xbox360)
£22.99 Pimp My Ride (Xbox360)
£13.99 Rockstar Table Tennis (Xbox 360)
£14.99 Tony Hawks - American Wasteland (XBox360)
All these games can be 5% off with the voucher code 'sale5', and a further 5% from quidco.
Some games have probably been posted before, but here's a list of what I found, and some havent been posted.