You can also think about doing Introduction to Mathematics through the CAP program offered by Melbourne Uni. It means you essentially do a single subject outside a CSP offer. THis means you can then move on to Calc One without Intro Maths taking up one of your (limited) slots.
However, CAP programs are outside HECs funding and therefore (I am pretty sure that) it will not be covered by HECs and you will need to pay the full amount up front (which is approximately 4 grand). What about finishing your B.Sci without completing all the necessary subjects then doing a post grad diploma and/or degree to make up for the remaining subjects?
I think that all of this seems far to time-consuming to consider as a possibility. Perhaps it would be easier if I looked into another University? If I understood what you are saying is that it will take a lot longer than 3 years to make even the slightest bit of progress, because after I've finished all my mathematics subjects I would have to start my b.Sci yes? which is another 3 years on top of the years of Mathematics subjects?
I was considering Computer Science @ Swinburne, even though Methods is a prereq, I could speak to the head of faculty and see what alternatives I could partake in. I know there are a lot of alternatives at Swinburne when it comes to Computer Programming.
Any thoughts on Swinburne as a University?
Do a computer science degree at monash. You just need 35 in further maths, and it's a little more direct than doing a science degree and then a masters of software engineering later. If you're a local, you get an opportunity of up to a $19,000 Industry Based Learning scholarship with an opportunity to work at a partner organization like IBM, Deloitte, Accenture etc - all arranged by the university.
Just a little something to think about - as you can see by my sig, I was in the same position as you once 
I would love to, but Monash is far out of my reach i'm afraid. I live in rural Melbourne, and Caulfield and Clayton are miles away from where I am. It will be a possibility if I can't find somewhere else though.
How did you find your Computer Science degree? did it cover topics well? how confident are you with your programming these days?