I can attest to everything Bones and others have posted... and if I were you Paolo, look hard at the 'couver, cuz you seem like quite the "outdoorsy" type of person. Lots more of that going on there, especially when mountain sports are involved.
Ontario (well, southern Ontario) is kickass if you're a city person like me. There are 'outdoorsy' type activites, but most of it is hiking, fishing, cross-country biking related, as Ontario has zero mountains... a few hills, but nothing crazy, Winter time drives me nuts cuz there's lots of snow, but no major mountains to ride in winter (everything is atleast a 6 hour drive away).
That being said Toronto is full of culture, and (on a world-wide scale) pretty clean. Montreal and ottawa are meere 5 hour drives away, TONS of concerts and the like always happening, lively bar scene, etc. etc. Live downtown and avoid commuting, because everything in the Greater Toronto Area is the perfect example of poorly planned Urban Sprawl. and being from Europe, you will hate the vast amount of suburbs surrounding Toronto. I've been told that downtown Toronto and Vancouver can be pricey for living, but you're from ENgland, so I wouldn't worry too much... I've lived in Toronto for about 2 years,a nd it was costly, but not outrageous.
Oh, and lastly, get used to the abundance of s p a c e. We have TONS of it, not like anywhere on that side of the pond (well, aside from Russia