It's fun to hear folks at the Abbey picking up British usage. We're pretty much all taking coaches rather than busses now, and we like our chips, bangers, mash, etc.
One person has decided s/he likes the word "knackered." At the end of the day, s/he will tell us s/he's "knackered" and do it with an amused smile.
I like "chuffed" myself, as I've mentioned.
"Chuffed" sounds somewhat friendly, while "knackered" sounds like you've just had an unfortunate experience at a butchers. Of course, a large percentage of experiences to be had at a butchers would be unfortunate from one point of view, I suppose.
I don't think any of us is "knocking up" our friends in the morning, and that's just as well.