At Tesco Express in Fleetwood, Lancashire, Energizer A23/MN21 battery 2-packs are 34p!!!
There were other types but didn't get chance to take a pic sorry.
I don't know if this is any use to anyone, but if anyone does use these, I thought it may be of some help, my OH bought these for his bite alarms for fishing and did leave some on the shelf too.
BB date Jul 2013