Since this is in the noob section I'm going to presume you're reasonably new to email marketing. Also, considering you're in Australia I'm going to guess you haven't looked at CAN SPAM act, or the Australian Spam Act 2003. For a definition of consent in your country, you can check this out http://www.austlii.edu.au/au/legis/cth/consol_act/sa200366/sch2.html
If you don't want to read it, the big point here is that 'consent' isn't really defined all that well in the US or AU. What this means for you is that someone submitting their email to you is about as much consent as you need. The idea of double opt-in is for ESP's to protect their ass from someone sending out massive lists of spammy addresses.
IF you collect an email address, AND you collect the IP and time, that is as much information as you need. Don't waste your time verifying opt-in if you don't have to.
