I found that living with a native English speaker in the same house does teach you a lot of intricacies of the language - pronunciation and grammar. However, it's a deep territory of diminishing returns. In Europe, everyone's English is kind of bad (a lot of people are fluent, of course, but almost never above the level you want to reach), so there are not many people to appreciate your fluency. I found it to be more enriching to learn a new language instead, that gives massive appreciation of the languages you already know.