After a couple of months of thinking on this, I suspect the film that Clauzy has in mind is UNDEAD (2003). Three survivors in the outback (a woman and two men, one of whom is her friend or boyfriend, the second shows up a bit later) fighting alien zombie things. The woman and the newcomer do eventually leave the primary location of the film and sort of go on a "road trip", but this is the very end of the film, iirc. Don't remember a heck of a lot of details, as I found this one dreadfully dull and disappointing after a lot of hype. However, it fits the time period and the plot details that Clauzy supplied....... wonder if Clauzy will check back in.......
Thanks a million for this, sounds on the ball will check it out and get back to you. Sorry was MIA