Well, as my name states, I'm a Canadian, and you're right, I am tempted to say that PRINCE2 is irrelevant in Canada, and you might be the only Canadian I know of wanting to become PRINCE2 certified, but since you're going to the UK, I think you've made the right choice.
In any case, PRINCE2 certification in Canada is handled by the US division of APMG international. So all you need to do is to email them at email@example.com with the following information: Your name, your phone number, your address, as well as a brief message telling them which test you would like to take (they are responsible for several tests other than PRINCE2) and the date by which you would like to take the test.
The test is really cheap, it's as low as $50.
According to the APMG, you may have to take the test in a public library or a university.
I think if you really want to do the PRINCE2, then your best bet is to seek a training company that will provide the training for the exam first, and then will let you take the test at the end of the training. This is better and there's a huge chance that you will pass the exam in this case.