http://www.greenmangaming.com/ are offering Grid 2 for £20, along with a further 20% off that once you apply their 666 event-specific code.
They're also offering for the next five and a half hours:
Bioshock Infinite, (regular priced but) with free NBA2K13, Borderlands 2 and Xcom: EU
Warhammer 40k Dawn of War complete -66%
Sins of a Solar Empire trinity: -60%
Codemasters Racing games: -75%
Virtua Tennis: -80% (£3)