(if this isn't cheapest let me know :) )
Sales Price: £10
Found this in Harrods HMV, a few left on the shelves when I saw it -
Not sure if this will be at other stores, but I was just wanted to notify anyone who was specifically looking for it, at a decent price (while shopping in central London).
I couldn't seem to find it for cheaper online (and in stock - ie. no Comets in stock or doing the sale price)
Oh and if you have hmv student discount even cheaper :D