Just got back from WHSMITH is Slough...they had dozens and dozens of these packs of batteries.
12 AA batteries for a quid, but they are also buy one get one half price, so £1.50 for 24. These batteries get good reviews.
May be store specific, may be national...who knows.....
These are way cheaper than anywhere online and have good reviews.http://i.imgur.com/5wiKezT.jpg
Just checked ...the best before date is 2023