Thats when you have to start using a dolly and a hammer... a good panel basher can do amazing things... I'm mediocre at best but would happily fly over to Oz on your ticket to give it a 'bash'!
Ask at an old established garage and they'll be able to recommend a good panel basher who may even do the work for beer and a local newspaper article to drum up business.
If you go at it yourself practice on some old scrap parts first... remember to put the dolly on the peak of the hill and use the hammer on the other side. Work in circles!
Mike