The Hut are selling "Dark Sector" for both the Sony PS3 and Xbox 360 for £24.93 (inc Del).
You can get cashback through the usual sites (e.g. 5% Quidco, making them both £23.68)
The next best prices seem to be £32 for the PS3 version (Zavvi) and £29.99 for the 360 version (Choices UK).
Become the Ultimate Weapon:
The virus. The source of your pain... your enemy... Your Power.
Unleash the deadly power of the glaive and become the hero.