Just a heads-up, I didn't buy it myself (will wait for it to come down even more!) - but my local Morrisons (Pinchbeck) have this priced up at £19.99 in the 'tech' counter. It's actually inside the glass cabinet where digital cameras, e.t.c. are stored. Obviously it's on DVD format, not Blu-Ray.
Cheapest I can see online is Blockbuster.co.uk @ £24.96 delivered?
[edit, scratch that, Play.com and Amazon are both under £18, just seems Froogle didn't pick them up. Probably not a great deal after all!]
I've no idea of the start / end date unfortunately :(