We usually use Morrison's, I had an unusual incident there a few months ago, but this could happen anywhere.
The petrol station was reasonably busy, and there was a chap working on one of the pumps with cones around it, so I was waiting for a free pump. Anyway, he beckoned me towards the pump with a thumbs up and started moving the cones, so I drove up to the pump.
I punched the button to pay at pump, as usual, put the card in and did the business, then checked that the pump showed zero, as I always do. I lifted the nozzle, went towards the car, the pump started up and the meter immediately clocked up an amount of fuel, before I even got the nozzle into the car. I put the nozzle back, and went into the kiosk to let them know.
After a few minutes trying to make them understand what I had seen, and them telling me it wasn't possible, I insisted they came out to look, and the repair man appeared too. I'd been charged for the fuel I hadn't had, and after much head scratching, they suggested I tried it again - and all seemed okay. They took my word for it and gave me the money back for the petrol I hadn't had.
I believe that the man working on the pump hadn't bled the air from the filler pipe before leaving, and certainly hadn't done a test pump. As soon as the pump started, the fluid compressed the air in the pipework and spun the meter. The bottom line here is - always check it says zero before you squeeze the trigger!