How does engagement and marriage effect a defacto visa?

My partner and i are already on a defacto visa in the uk. im australian and he is from the uk. we are planning on moving back to australia permanently and will be applying for his defacto visa to do this. at this stage in our relationship, we are not ready for marriage, but we are wondering what the rules are if whilst he is on the defacto visa in australia we decided to get engaged and married. how would this affect us?? thanks for any help.How does engagement and marriage effect a defacto visa?
If he comes to Australia on a de facto visa, and you get married, it will not affect anything because there is actually no such thing as a specific facto visa. You apply for and are granted a spouse visa (sub class 309/100) and it just happens that both married and unmarried partners are eligible to apply if the de facto partners have lived together for 12 months or more. If you get married, it only strengthens your claims to having a 'genuine and continuing' relationship. You have nothing to worry about.