UPDATE.
I now have batteries, I was wrong about Tesco, they did have them, just not at the Pharmacy (silly me for thinking logically and actually asking the useless fucking idiot behind the counter at the Pharmacy).
I found them with the rest of the batteries, shows I wasn't thinking like Mr Tesco. They were reduced, too, to £1/pack of 6, so I bought every pack they had (5). I will now restock my stashes.