Here's a list I've compiled over the last two days of PC World's current games sale prices, along with recommendations for what makes more at CeX ;o) Most info is taken from other posts on this site, PC World's site, and instore at PC World. Please add to it :o)
Bold is recommended, italic is only recommended for exchange. All CeX prices are cash unless stated, and remember they change but usually only monthly and not by much. And the list is in the first comment as I can't alter colour/bold text in the main post. Sorry.
No guarantees you'll get them instore either, or at the below prices, but do check them at the till just incase.