Canon UK: spammers

I bought a new lens for my Canon camera, and sent in the registration card. I put in my email address because they said they'd give me their "Imagine" magazine which I thought might be useful (the "EOS" paper magazine apparently is). But it turned out not to be, so I unsubscribed - to no effect. So, much as I like their cameras, I'm pissed off with them now. Wonder if I should bother writing a complaint in snail mail?