petrol gauge just dropped as i was driving

[speazzzzz]

was driving along and my petrol guage dropped into red, put about 30 quid in to the tank and gauge didnt move  " please refuel"....i have checked the fuses and the needle come up to a certain point so there is power. i am sure it is the sender in the tank but how do i get access in a mark 4 ?

any ideas ?

[>>Mart<<]

i have not checked but im shure if you pull the seat base up on the rear seats there is a large plastic cap and the fuel tank/sender is under there