This will probably become 0 to frozen in no time, but thought it may be worth the mention for those willing to take a look.
Shopping at Sainsbury's Ladbroke Grove, and noticed they had a stand near the click and collect counter with BOGOF on the normal AAA & AA 4 pack Duracell Ultras. However, they also had the 4 + 4 packs on the same stand. This could mean 16 AAA batteries for £4.49! I didn't see any AA 4 + 4 packs though, so can only speculate that offer. I didn't buy any myself, as have a huge amount of Energisers from the Argos deal, but worth investigating if you happen to shop there. Not sure if it would be nationwide either, but keep that in mind next time you shop there.