Oh dear that doesnt sound so good, my brother said his petrol cap locking failed a while ago, and the spike has been flapping around loose in his boot ever since. The weakening pump sounds about right too, as the problems been intermittent but getting more common, to the point where when I was looking at it yesterday it wasnt working at all!!
Ah well, I'll check for leaks then if that yields nothing I'll replace the pump. Any good ways of checking for leaks?