Make sure to check out the clearance area that they will have, most stores have on or two end aisles dedicated to it.
I've just picked up NOW TV boxes for £5 from my ASDA Local. They had clearance stickers on them. NOW TV has once again repackaged NOW TV boxes and ASDA is clearing out the older packaging, probably see other retailers clearing out too.
Obviously a wild goose deal, but if you're going to ASDA worth looking out for.