Sorry I don't have too much information but I just saw this advertised on TV - 20 standard sized (275ml) bottles of becks down from £13.99 to £6.99.
Possibly the cheapest I've ever seen. Where I work we sell this for £3.60 PER BOTTLE!
I've never shopped online with Sainsburys but I assume it's available for home delivery, but it would definitely be in store - Offer ends 23/09/2008
Sainsburys also have loads of good half price offers at the minute so it's a great time to get yourselves down there!