I’ve been looking around and this is the cheapest that I’ve seen them for so far.
A few other places I previously tried were: Play.com £14.99, Playasia £12.75, HMV (instore) £17.99, Gamestation £14.99, Game £14.99, Game (instore) £17.99, ToyRus £15.99 (instore) etc etc.
£11.99 for a decent controller sounds v good to me!