Gunnar said:
You don't need to be registered to vote. You have to show up at the polling station with ID. That's it.
(Not that the "scrutineers" were checking ID anyway. I could have taken all the voting cards from my household and voted multiple times.)
I was working the election, and during training was very surprised how trusting the system is. If you're on the list as registered, you don't even need ID. All you do is show up at your poll, state your name, and if you're on the list you're good to go. If someone challenges you, and you forgot your ID at home, no problem: there is an "oath of qualification" the Deputy Returning Officer (the job I did) can have you swear/affirm stating that you are the person on the list and eligible to vote.
If you're not registered, then yes, you need something that proves you live in the right area for the poll. Regardless, it is very easy to get registered the day of. Just walk in, flash your drivers license (which has all the info they need to fill out the registration form) and you can now vote.
Oh BTW, you could not have voted multiple times. Those little voter cards you get in the mail don't mean crap. All they do is let you know where to vote, and make things very very easy for the election staff (easy to find a name on the list, or figure out you are at the wrong poll). All you need to do is state your name, and the poll clerk crosses your name off of the list when you are given a ballot (name crossed out = can't vote again). If you get caught trying to vote twice you can actually be arrested by the deputy returning officer, fined and/or imprisoned. They will usually just order you to leave the building immediately - you won't get arrested unless you decide to try and stick around (other things that can land you in jail: applying for a ballot in the name of another person and attempting to vote knowing you are not qualified as an elector).
And no... I didn't forget to vote. Spending twelve hours sitting only two tables away from the poll I'm registered to vote at it would be a bit hard for me to forget.