I think you might have the Liberals confused with someone else, there social policy is not precisely Libertarian (its Replublican-ish,), nor are they a single issue party, they are essentially the ruling half (at the Federal Level, at the state level the Nationals sometimes lead) of our Liberal/National coalition who represent the Conservative side of politics here.
The Social Democrats have not to my knowledge ever held the balance of power (in fact I'm not even sure if that group exists?, I know there are both Labour Democrats and Liberal Democrats), you might be thinking of the Democrats who held the role the Greens currently do (ie the largest party not part of the 2 major groups), up until the late 90s. We have a bunch of parties who feature the word Democrat in their titles, some because they were spin offs of the Democrats, others because it seems like a nice word to have in your title in a democracy.
Also there's not really a Christian Conservative single issue group, there's 2 parties playing that card at the moment Katter's Australian Party (which is new) and Family First. The 2nd is actually pretty much a Christian Conservative group, the former is hard to explain, since he span of one of our major Conservatve Parties his policies are pretty wide ranging but largely conservative, in favour of farming and hunting , and Christian.
Sorry if you were trying to describe ideologies rather than parties but since some of party definitions and names are very different (Our Liberal Party would usually be considered Conservative) I felt the need to qualify.
Disclaimer: I don't care much for any of the major political parties at the moment, but my social positions are Left (significantly left of even our Left party really), I apologize if my bias has slipped in anywhere, I tried to be as factual as possible.