Don't sweat the small stuff, man. Finding addresses in European cities can be damn near impossible as there are no rules. The proper address of a building could be defined by the street, the square, the intersection, the river/canal, the island, the neighbourhood or even the single building. Just imagine trying to find “Cityplace 6â€, “Ward’s Island 17â€, or simply "Architecture Building, University of Toronto" with no street name or number needed. In some places in England you address letters based upon the name of the house rather than its address, for example my aunt's former address was "The Corner House, St. Catharines Road, Townname, Herts." I’ve been told that in Japan buildings are numbered in the order they were built.
Anyway, looking at your Spadina example "Lower Spadina" is an extremely short distance and I believe it only has one building fronting on to it so it's extremely unlikely that that would ever be an issue. Independent Spadina Cres addresses only apply to buildings contained within the crescent (it would be difficult to number the building otherwise), and that only applies to one building: Knox College. Buildings on the outside of the crescent are continuous with the numbering on the rest of Spadina Ave; 507 Spadina Ave and 507 Spadina Cres is the exact same building (computerised systems like Yahoo maps or Google maps get confused by this). In a real-life situation 99.9999% of the time the only confusion that you will experience is the Spadina Ave/Rd distinction.
What seems to confuse people far more is the University Ave/Queen's Park Cres/Queen's Park (with no designation) distinction. I always hear people referring to the ROM as being located at University and Bloor, but if that's what it takes for people to best understand how to get to their destination... whatever.
Personally, I enjoy little quirks like this; they are part of what makes the urban landscape so interesting.
