Tesco Entertainment currently have a discount code available, which will knock £5 off any purchase. This opens up some fantastic pre-order deals. I've posted a few below, but if you find any more, please post them in this thread:

Call of Duty Modern Warfare 3 - £34.90 - Call of Duty - Modern Warfare 3 - Microsoft Xbox 360 - Free Delivery - Tesco Entertainment
The Elder Scrolls V - Skyrim - £33.90 - The Elder Scrolls V - Skyrim - Microsoft Xbox 360 - Free Delivery - Tesco Entertainment
Batman - Arkham City (Joker Steelbook Edition) with Tesco Exclusive Joker's Carnival Challenge Map - £34.70 - Batman - Arkham City (Joker Steelbook Edition) with Tesco Exclusive Joker's Carnival Challenge Map - Sony PlayStation 3 - Free Delivery - Tesco Entertainment
Batman - Arkham City Collectors Edition - £50 - Batman: Arkham City (Collector's Edition) - XBox 360 - Free Delivery - Tesco Entertainment
GoldenEye 007 - Reloaded - £34.90 - GoldenEye 007 - Reloaded - Microsoft Xbox 360 - Free Delivery - Tesco Entertainment
Battlefield 3 Limited Edition - £34.90 - Battlefield 3 - Microsoft Xbox 360 - Free Delivery - Tesco Entertainment

EXM5OFF30-1 is the code and it can only be used once per account, but you can setup numerous accounts The best thing is delivery is free and your purchase is usually with you before release date

Using Top CashBack with any of these deals, will earn you a minimum of £2.80 cashback (cashback is 8.08% of the final value)!