M&S have a selection of Blu-rays at 2 for £10; each are individually stickered at £15 but go through the till at a tenner.
The following were available at the Teesside Park store:
Burn After Reading
These were all previously part of the two for £18 deal, which appears to still be running online.
UPDATE: Bookie has kindly pointed out that if you add these online they do checkout at £10 too!