I know some have been waiting for this Special Edition to finally drop under a tenner. I also know that HMV have been having a lot of financial problems of late, but they have been pretty reliable online upto now. The price's elsewhere do not seem to be anywhere near this one.
Also note that the DVD + Blu-Ray Edition with DVD packaging is £12.39. If you want the one with Blu-Ray packaging Amazon are the cheapest. Again at £12.39.
By the way, don't forget Quidco/TopCashBack. Over 5% with the latter!