I've noticed that HMV are getting rid of their budget PC games for silly prices, but up until now they've all been pretty terrible games. However, I spotted this gem in the Trafford Centre this morning. I already have it, but it is an excellent game that I would have had no hesitation in snapping up for a quid otherwise. There were four left when I was there.
Chances are this is nationwide, but it will depend on whether your store has stock of this.