CD-Wow recently ran a £5 discount voucher against a select list of games.
The only title I can see at a particularly competitive price is Pokemon Diamond for the DS which would be £11.99 using the voucher code.
(The next best price appears to be £23.99 at Powerplay.)
I already have this title and no intention of using the voucher before it expires (24th May), so the first person to PM me can have the voucher code.
Don't forget 4% Quidco.