But on this occasion it kept going, right up to £7-odd and then overflowed down the car and onto the ground

It was level wit the fuel filler cap and spilling out all over. Obviously I immediately put the nozzle back in its holster.
I walked into the garage and told the guy there's quite a large spillage of fuel out there. He just said "oh. It'll be alright". No offer to put sand down or attempt to clear it up! No instruction to make me do so! I asked him if there was anything to get the extra fuel out or anything, and he just said no :|
So I ended up rocking the car, spilling fuel all over the car and ground. Naturally I used the paper towelling to clean the car and try soak some of the fuel up so I could get the cap on properly, but balls to the ground. That's his problem. How can petrol station attendants be so, well, useless? Isn't it dangerous to have a quantity of fuel on the ground? Hence the sign saying "notify attendant of any spillages"?
Ah well, after 140ish miles I've still got over half a tank of fuel left, amazing
