I don't know if they have a name - I thought they used to be called change machines, but the coins would be out of legal tender by the time the right amount came out. The machines which are full of 2ps or 10ps and you put another one of your own in, at which the machinery sweeps it into the pile of coins, as well as the odd 'gift' which may well cost less than any one coin, which move on another millimetre and nothing falls out.
When did they become so popular? I was in an arcade today and there were loads in there. Who uses them? What are they for? The float expenditure alone must be putting some arcade owners out of business.