I went and had a smell of his car the smell is coming from the rear wheels (both sides), no smell inside or in the boot. no leaks or puddles on the ground.
very strange! could a pipe have come lose? he says he never fills the tank to the brim.
It could be the fuel filler neck, the fuel line to the engine or the return fuel line? If it only eminates from the brear, then at least you can pin point.
Have to get it up on a lift and start an extensive search.