Once, at an off-license in Brixton I bought two decent bottles of wine. They cost about 18 quid. The cashier was far too busy talking to a mate to pay attention, and I had to wait for her to bother to serve me. She was using an old fashioned till, which somehow allowed for the following - I gave her twenty quid, she rang up the amount, and then rang it up again, and then kept the change, and gave me back the cost of the goods. The service was so shite that I didn't bother telling her.