An intermediate fix is to get an electronic egg timer. I know roughly how long it takes to fill my tank, so when I start filling it, I set the timer and when the amount of time has elapsed, it goes 'ding ding ding ding ding ding ding', and I go to my van.
It means I still have to hang around for a few minutes to get it really full to the brim, but it stops the water overflowing into the footwells of my van!
