When trading some games in, goto GAME first and ask how much they'll offer you for your games. Ask for a receipt to prove it and then go along to Gamestation. They will beat GAME's offer by £1 for the whole lot.
Tell the person behind the counter at gamestation you're quite happy to bring in each game separately to get an extra £1 per game and they will do you £1 extra per game just to save themselves hassle.
I did this today, GAME offered me £44 and Gamestation offered to beat it at £45. I only had 3 games but said I'd bring them in separately to get a extra couple of quid. They then said they'd just do it for me and gave me a credit note for £47 to save themselves the hassle of doing each game separately.
It's not really a deal, just a good tip when trading in games!!