Christmas is All Around: Love Actually, Questions and Curiosities (Pt. 2/2)

As we've already seen in part one, Love Actually has a lot of threads running in just about every direction imaginable.  There are so many nuances, plots, characters, and connections to appreciate, especially if you're a repeat viewer like myself.  Here are some of the things that always come back to me:


The connections:
This may be bordering on unrealistic (London's not that small, after all), but so many of these characters have ties to one another, and half the fun of watching this movie is trying to track all of them.  For example, Karen's brother is Prime Minister David, whose love interest Natalie is next door neighbor to Mia, the slutty secretary hell bent on seducing Snape Harry, who just happens to be married to Karen, who is BFFs with recently-widowed Daniel... You get the idea. 


Unclear connections:
Jamie (Colin Firth) and just about everyone. Juliet, Peter and Mark meet him at the airport in the end, and Sarah seems to be sitting with him at Peter and Juliet's wedding, but his ties to them are unclear-- are they all just friends/acquaintances?

Unrealistic lifestyles: 
We see a lot of the characters at their respective jobs throughout the film, and I have to say, I'm not sure they'd all be able to afford living in central London in, let's face it, some pretty snazzy digs.  Sarah, Harry, Carl and the gang work at what I've determined is either a magazine of some kind, or a non-profit organization (or a magazine for a non-profit, I guess); Juliet appears to maybe be a fashion designer (although she is the most consistently terribly-dressed character in the film); Mark...makes movies, I guess, though he also works in an art gallery?  Anyway, they're all very artsy and eclectic, but I have to wonder how likely it is that so many creative types can swing the ritzy-looking lifestyle they have in this movie.  But then again, maybe a bit of a posh appearance comes with the British accent and the crisp look of London.

Lingering questions:
 Where exactly is Carl from/what is that beautiful accent?

What is ailing Sarah's brother? His few shown behaviors in the film don't seem to point to anything definitive.

What exactly is going on behind the scenes with Harry's affair? When does he actually find the time to sleep with Mia/give her the necklace, etc.?

Are we supposed to be happy for Karen and Harry's apparent reunion at the end?  Because I'm not.  I get staying together for the kids and all, but there's a kind of deep discontent evident in that final exchange that just leaves a bad taste in my mouth.

Why, exactly, is Colin in this movie?  I mean, it's good for a bit of a laugh, but nearly every other story line teaches a lesson or sends a message about love.  All we learn from Colin's misadventures is that American girls are sluts, and lots of us have Southern accents (usually corresponding with an uptick in sluttiness).

Why does American Joanna (who has the singing voice of a goddess) attend Sam's school in London, especially when she apparently has a home in the U.S.?  I mean, obviously, it allows us to have the almost-too-exciting rush to the airport scene, but other than that, this seems a little strange.