I assume you have your ETA organised? Also, there are rules regarding applying for various visas to stay in Australia whilst you are located there. I am under the impression that just because you marry an Australian ,you do not automatically get the right to live there permanently. I think, and I may well be wrong, that an spouse visa in your case will be issued with a 2 year validity. At the end of this time, you have to prove the relationship is continuing, and then it is extended for another 2. After this, I think it goes to a full PR, although after 2 currently, soon to be 3, years of residency, you can apply for citizenship.
Take it from someone who has emigrated to Oz, it's not as simple as packing a bag and buying a ticket. The DIMIA are a real pain to deal with, and they take a very hard line on immigration compared to the U.K.
The australian govt will NOT deport you because you have a bit of debt in the U.K. People like interpol are really not interested in your debts. They have far bigger things to be concerned with.
As an aside however, and bearing in mind I don't know much about you, your situation and you mother, I do think it's a bit harsh to dump this all on your mum. Sounds like a bit of a whim to me, and you need to think carefully about shafting the person who has raised you, and whether it is all worth it. If it doesn't work out in Oz, you'll face up to all these problems when you have to return to the U.K. They won't just go away. Problem then is, you won't have anywhere to live. I wouldn't put you up if you'd done this to me.....