What ever you do DON'T miss the Ace Cafe, you'll kick yourself if you don't go. I've been there many times and it's brilliant, as is the food. Try to go on a themed day if you can, all the information about these themed days can be found on the Ace Cafe website. You may already have the link to the website but just in case you don't here it is
http://www.ace-cafe-london.com/default.aspx, another place that you should consider is The London Motorcycle Museum it's 4 miles from the Ace Cafe and again is worth a visit, here is the link for more information
http://www.motorcycle-uk.com/lmm/beginning.html. Another one to consider is the 59 Club this is aproimatley 17 miles from the Ace Cafe, here is the 59 Club website
http://www.the59club.org.uk/ The following link is to the location and opening times of the 59 Club
http://www.the59club.org.uk/address.html. Another place that you might like to visit is Ace Classics
http://www.aceclassics.co.uk/ about 18 miles from the Ace Cafe.
A dealer that might interest you is Jack Lilley website coming up
http://www.jacklilley.com/ I've never been there but the range of goodies that they have in stock is by all accounts massive. When are you going to be in London and what date will you be departing ?, the reason I ask this is because if I find out about any more events that I think that you might like to see I can post them here for you before you go. One thing, and this might surprise you, don't forget your brolly

and with all this rain we're having at the moment, you also might want to consider a rubber dingy as well.
I don't live in London but if I can help you out in any way feel free to ask. If I don't know I'll say so, the last thing that you'll need is duff information from me.
One last thing if you go to my home page and look up the albums section, you'll find lots of pictures of the Ace Cafe and the Brighton Burn up, this I'm sure will wet your appetite.
Also there are 2 great books that you might want to take back home to Canada with you, one is The Ace Times ( This is a hard back book and in my opinion is one of the best books I have ever read, make room in your suitcase for this one ) and the other is a bookazine called Celebrating Ace Cafe Culture- London 75th Anniversary here is the website for more information
http://www.mortonsbooks.co.uk/acecafe.htm Both should be available to buy at the Cafe.
Hope that this helps you out