We picked up the 2 disc version of the latest Harry Potter DVD in the 5 for £30 offer that is on in Virgin Megastores at the moment. I believe this is included instore rather than online. I've been waiting to get this version cheap for ages.
There are plenty of others in the offer that may be of interest. We also picked up the following:
Little Britain Series 3
Ghost In The Shell 2: Innocence (2 disc)
The Last Kiss
DOA: Dead Or Alive
House Of The Dead
A Scanner Darkly
They had plenty of other decent DVDs in the offer. It's well worth a look.