Just looked around town and found Red Dead Redemption (Xbox) at HMV bundled with 800 Microsoft points for £39.99.
Cheapest I can find 800 MS points online is around £10.77 to £10.95, making the game around only £29. Let me know if you can get them cheaper elsewhere.
Only a good deal if you want MS points, otherwise the game is £34.99 on Amazon and other similar sites. This was in the Newcastle Upon Tyne store but presume its nationwide.