Other mistake: Considering how long the Prime Minister's car is parked outside in front of the only road into the school, where there is to be the school Christmas concert, it's surprising how many cars are still trying to find a parking space. Also, you can see that suddenly no cars are driving when Natalie gets out of the Prime Minister's car.
Continuity mistake: When Juliet and Mark are at his flat there is a tall metal self-standing hanging rack and a tall black art canister directly in front of certain canvases and frames. As Juliet inserts the video in the wide shot, the rack and canister are gone. Yet, in the next shot they are back. (00:52:45)
Harry: Tell me, exactly, how long it is that you've been working here?
Sarah: Two years, seven months, three days and, I suppose, what, two hours?
Harry: And how long have you been in love with Karl, our enigmatic chief designer?
Sarah: Ahm, two years, seven months, three days and, I suppose, an hour and thirty minutes.
Harry: I thought as much.
Sarah: Do you think everybody knows?
Harry: Yes.
Sarah: Do you think Karl knows?
Harry: Yes.
Sarah: Oh that is bad news.
Harry: Well I just thought maybe the time had come to do something about it.
Sarah: Like what?
Harry: Invite him out for a drink and then after about twenty minutes casually drop into the conversation the fact that you'd like to marry him and have lots of sex and babies.
Trivia: Billy Bob Thornton agreed to appear in the movie without having seen the script. On the day of shooting he told director Richard Curtis that he was scared of Benjamin Disraeli's facial hair, and as such wouldn't be able to do the scene in Ten Downing Street because there was a picture of him on the wall. Curtis told him to keep his back to the picture throughout the scene, which he does, although you'll notice he looks quite nervous.
More questions & answers from Love Actually
Answer: It's because of the complications that Sarah was having with her troubled brother. Apart from that, who's to say they don't eventually get together?
Hamster ★
In the follow-up short film (the Red Nose Day special) we learn she eventually gets her happy ending with a man played by Patrick Dempsey.