Dark Sector on the PS3 and 360 is released on Friday but shopto have it instock right now and are selling the PS3 version at least £3 cheaper than any other retailer.
Shopto promise to dispatch all orders completed by 5:30pm the same day and 99% of orders arrive the following morning (which is stated on the site and has been my personal experience as well), so you'll receive it 2 days earlier than anywhere else.
Don't forget to go through Quidco to receive 4% cashback, to make this even better value, making this just £28.79 including recorded delivery.
The Xbox 360 version is also available at the same price if anyone is interested but the PS3 version represents better value. :)
Hope that helps. :)