I have now fitted a new rear-door lock and fuel-gauge sender gasket. I had a look this morning and you were right about where the smell of petrol was coming from, it had leaked all over that area, the recess was very wet. I dried the area carefully afterwards and took the little gem for a run up and down a few hills with a full tank. When I got back the recess was still dry although I dare say the petrol smell will linger for a while.
You were also spot-on about the cost.
You see, that's why I'm on here, all this expertise available for the asking.
Thanks again,
