Hmm-- well, it looks to me now as if it is very individual, Kooyeen. Some do and some don't.
As long as we're on the topic, I might as well go on to say that I have been making a (small) point of teaching '
hundred 'n'...' as 'natural English' to most of my students. In addition to my own habit of doing so (could it be a Midwest American thing?), I have been using the excellent textbook,
Listen Carefully, by Jack C. Richards (Oxford U Press), whose accompanying cassette also (as you said, in BrE) presents the '
hundred 'n'...' form.
In light of Jim's comments, however, I think I will drop this exercise.