Fuel left in tank when car states 0% remaining
If this helps anyone:
My car's "miles left" showed 0 and I travelled an extra 1.5 miles to the fuel station.
I filled 48.5 litres (maximum it would take)
The tank holds 53l.
This means I had 9% fuel left.
I did 409 miles, so I could have done an extra 36 miles.
Basically, it appears the car has roughly 10% fuel remaining when it says 0% is remaining.
I've only tracked it once. I'll do it again next time I fill up and update this post.