estate fuel tank seals?

[pondweed]

D9 fuel tank on HDi 99
put up rear seats to make a full load bed, and noticed the rear seat squabs were damp with diesel where they lean on two round rubber bungs under the sound insulation (this was all damp with diesel) No smells evident up until I raised the seats.

I know that the car had had its pump replaced and that they had dropped the tank again afterwards as there were leaks. Not sure where as only have invoices....

Is this a common problem (I've been brimming it so can get fuel mpg figures recently) and should I do anything to fix it easily? or live with it.....