Noticed this one in the Trafford Centre (downstairs store) this morning. It was for the 360 version only; checked the PS3 edition and it was double the price. Outstanding price for the Death Edition. There were two left when I was there.
I obviously have no idea whether this is nationwide. It seems slightly odd that the different console versions were different prices, though this 'sale' sticker was the newer blue one and GAME have been getting rid of their collectors editions recently, so it could well be across all stores.
UPDATE: Early indications suggest that this deal is indeed nationwide.