I am not sure how this works as I just discovered it so any guidance will be helpful..

I am on a temporary residents visa in Australia and have 2 houses in London which I rent out, both of which have been primary residences at some point (I remortgaged the first as a buy to let and pumped the cash into my second which I stopped living in 3 years ago when I moved to Australia - one year on a tourist visa, 6 months on a 457, 1 year on a student visa and now I am on a 475 temporary residency visa). As a temporary resident I understand the Australian government looks only at money earned in Australia so if I sell my UK properties and do not return to the UK for 5 years can I avoid the CGT payments on these? Must I sell both to do this? Is there a clause whereby I can live in one or either of them for a period of time to remake that a Primary residence and hence solve the CGT problem? I would be delighted if anyone can assist me..