In Wilkos today I spotted packs of Duracell plus batteries (AAA were 4+4 free, not sure if all other types had the 4 free) on offer at 2 packs for £3.48. The offer was on AA, AAA, C, D & 9A.
So I managed to get 32 AAA batteries (4 packs) for £6.96 or 22p per battery!!!
Thanks to BargainHunter09 on MSE
It is online, but not with the 4+4free