Have you checked the passenger side fuel-tank pot hasn't popped apart?
In case you haven't come across this before, the top section to the pot is a bayonet style fitting to the bottom. Lifting the pot out of the tank you can see a ring halfway down it. Push together and twist clockwise. On occasions the seal inside the pot splits, this iirc used to be available with the internal fuel filter from Rover (if you can find a dealer).