Modern buildings in London seem to have got the soundproofing right; of course you'll pay for it but it's worth it IMO. I live in a shared ownership (housing association owns 75%, me 25%) flat and it's completely quiet (the tradeoff is that I'm living in Tottenham as that's the only way to make it even vaguely affordable).
I think the small-talk-with-everyone-you-meet thing is a characteristic of very small towns and villages. I've lived in medium-sized places that didn't have it. The introvert ideal of a blissful hermitage miles from anywhere is probably impractical, for many reasons, but I still have some faint hope of finding a liveable middle ground someday.