In the 1950s and probably the 1960s many UK large shops had a central payment point. The customer didn't have to change queues though.
In the Co-op (Co-operative Society) grocery store each counter had an overhead wire on which little boxes whizzed back and forth across the shop to a distant eyrie where the money was handled. Your money and bill was put into one of the boxes - and the assistant pulled a handle to make it move. Then your change and receipt returned the same way. If your family had shares in the Co-op then you had a personal "divvy" (dividend) number which was ingrained in your mind - a bit like a loyalty card discount nowadays.
In some large department stores they used the vacuum tube (not thermionic) system. Your money and bill was put into a short metal tube container - which was inserted in a hole in the wall. A hiss and it disappeared through a labyrinth of tubes to the accounting department somewhere in the building. Then a clang when it returned with the change and receipt.
Can't remember if the assistant was single-threading with one customer during such an exchange.