Would I (A landed British imigrant) be considered a Canadian citizen now because my wife is Canadian?
I’m pretty sure that marriage does not grant automatic citizenship in Canada… although I am not expert, so I wouldn’t take my word for it.
Once you’ve lived here for a certain length of time (3 years in my case) you can apply for citizenship… the test they give you is a piece a piss if you take a couple of hours to read over the material… and you can keep your British passport as well… which makes travelling so much more convenient.
Since you are already a landed immigrant nothing changes because you married a Canadian. I married a foreigner and sponsored her to become a Canadian landed immigrant. She had to undergo a medical and a police check in her homeland before she got her landed immigrant papers but she still has to live a full three years here and do the necessary things to become a citizen.