I did not assumed it was wrong, I was just wondering if it was, since I speak Enligh for almost 10 years now and I have never seen it, even though I read a lot in English in the last 3 years. That's why I asked if it was indeed correct. My English is getting better because of the Norwegian course, so I kind of have a 2 for 1 deal. ;)
My feeling is that any sentence with "one" in it, meaning some un-named person, is 19th century upper or middle class English from England. I understand it and use it when I want to be a little pompous. "My own room" or "Her own room" etc would be much more common in speech one thinks.
I would somewhat disagree. As a native speaker, I would agree that using the "one" structure to mean an impersonal subject sounds slightly more formal or proper, but in no way does it sound archaic, old, pompous or specifically British. It's very normal, just slightly higher in register than the alternatives.