The first time I charged at a public charge-point I sat in the car while it charged. I think I got out, didn't lock the car, did everything to start the charge, then instead of locking the car and walking away, I just got back in again and sat down. The charge went right on charging.
On another occasion I hooked the car up to an Instavolt and went into the attached shop. I probably locked the car at that point, but when I came back to the car I wanted to put the stuff I'd bought in the boot so opened it to do that. For some reason I got back into the driver's seat before I disconnected the charger - maybe I just wanted to see how much charge it had. Anyway, the radio came on and it was a piece of music I really like so I sat there for about ten minutes listening to it, and watching the car get itself up to 95%. It was still charging reasonably quickly even then, although it's an SR and this was only a 50 Kw charger.
The only thing I ever did that stopped a charge was when I unlocked the car and opened the door to fetch my camera, while it was on the granny charger. I didn't actually get into the car on that occasion. That stopped it, and I had to unplug the connector and plug it in again to get it going again.