Almost every time I went into our (former) local Starbucks, I'd hear American or Canadian accents, but some of those were tourists. From what I understand, most Americans sort of congregate in North London or Chelsea. Oddly, most yanks from this board in London aren't living in either.
I thought I might find a lot of Americans in our new area because some of the selections in the market are very American friendly and there are some UK-Yanks who live around here, but so far, I've run into none when I've been out and about.
ETA: I only went to Starbucks a few times in the US, but here we (used to) go because they are relatively consistent, offer things like eggnog lattes, and serve filter brewed coffee. If you told me a few years ago Starbucks would someday become a regular part of my existence, I would have told you you were nuts. It's not about familiarity for me, but we absolutely needed a place to get out of the house sometimes, we aren't frequent drinkers, and Starbucks was the only coffee shop that was open sort of late other than Nerd.
ETA2: Our former building always has either a Canadian or American in it. I was the only American in it for a few months last year, but some American girl moved in just as we were moving out. Not sure why it worked that way, but I always thought it was weird.
