Our disappearing fivers

OK - so that is an extreme example, but 5 pound notes in the UK have gotten to be in a terrible state. Everytime I get one (only as change in a shop - never at ATMs) it is invariably crumpled, dirty and obviously old. Now I know why. Banks are not using them, new notes are not coming into circulation and everytime I want to buy a newspaper I have to use a 10 or 20 pound note and walk out of the shop with a load of pocket-busting pound coins. Grrrrr.