This is correct, but if we're being pedantic (it is HN after all) the locale code for the UK is "gb". The language / locale would be fr-gb.
I work on this sort of thing for airline ticketing pages. fr-gb would mean the customer wants the page text to be in French, but they want to buy a ticket using the UK system (i.e. Using GBP instead of EUR as the currency if possible, and all the formatting differences that would be specific to "gb").
Quick edit: technically I guess your locale doesn't have to determine your store region, that's just how we do it. As far as I know there's nothing except development effort preventing us from allowing someone to book a flight in French, using GB locale, and with preference for the Japanese point-of-sale system.
