No wanting break the rules on advertising here, but thought I'd share a wee find.
B&M are currently selling blister packs of 6 Panasonic CR2032 batteries that are suitable for Disco key fobs (and probably others) for £1.99.
Elsewhere you'd pay more than that for a single battery if you want a well known brand.
I know the pound shops often have big cards with many batteries of different types very cheap, but generally they're unknown brands and half the sizes I never use and when I get round to using the ones I can they're often out of date and dead.
Duncan