Note that some Star Alliance airlines have been introducing the chance to upgrade with miles on other *A carriers. This seems to be rolling out alliance wide, and by next May there is a chance that you might be able to upgrade AC flights with miles.

Other option to consider is Air Canada Club Class, offered from Manchester to Toronto. This is domestic Executive Class seating (a wider version of World Traveller Plus) for premium economy prices. They would get priority check-in and lounge access, though would be stuck in economy on the Toronto-vancouver-Toronto flights.