I haven't seen anyone do it to get annoyed (presumably because the phrase is used more in US).
What do your newspapers call it? I guess you could call it separation. In the US the adjective "separatist" is used to modify the noun "movement" such as when discussing Basque political activism or South Sudan, but the act is almost always referred to as secession.
Incidentally, I don't recall any newspapers or magazine writers substituting succession for secession. I only ever see that mistake on this forum, and only from a few posters, but many of them make it in a way that it comes off as ironical, because the mistake is usually made when someone is talking about a US state legislature taking it upon itself to gain independence from the federal government. You get comments like: "Obama says we should not return to the way things were. He's wrong. That's why the succession movement is so popular." (note the paradox.) Well, that wasn't very good really. I'm trying to make one up. There was one post, and I forgot its author, but he typed succession for secession. Clearly he meant secession, but if it was read literally, then the post had the opposite effect than was intended. It was positively delicious.
