An article relating to this blog post on Finextra:
Bank Machine rolls out £5-only ATM
As growing numbers of customers tighten their belts amid the economic slowdown, UK independent ATM operator Bank Machine is rolling out a network of units that only dispense £5 notes.
See article
I associate fiver-dispensing ATMs with cash-strapped student areas - I think that's where I last saw one. And that was some time ago.
By contrast all the ones around here only seem to have 20 quid notes in them - although they don't tell you that until you've asked for 10 or 30 pounds - or some other amount they can't dispense.