[the_third_wave]

I moved to Sweden from the Netherlands - i.e. another Germanic-language country just like (most of) the U.K. - and learned Swedish quite rapidly. I may use a non-Swedish word every now and then for something for which I do not know a Swedish term or where the Swedish term does not cover the concept I'm trying to convey but I do not "just use English" other than with my (Swedish) wife [1] which makes it far easier to join ongoing conversations without causing a stir by using English. Sure, most people speak passable English here but breaking into a conversation in Swedish using another language does tend to break the flow and changes the discourse.

[1] I'm Dutch, she's Swedish/French, when we met she lived in the U.K. and did/does not speak a word of Dutch nor did I speak any Swedish. I learned Swedish by myself but hardly ever use it at home other than when my children have friends over - I speak English with my wife, Dutch with my children and Swedish with the rest. Both children went/go to a French school to make the picture complete.