This may be store specific but worth a nosey - Clearance section in the Rhyl store has quite a few packs of 20 AA Duracell batteries for £3. I also spotted a few packs of the AAA batteries for 50p and other batteries from 50p - £2. All marked with the clearance sticker.
Boots Clearance - 20 x AA Duracell Batteries - £3!! 4 x AAA Duracell Batteries 50p