I think in the UK they use "love" like the Southern US uses "hon", to address just about anyone, but it's rarely used that way here.

I've been told that in the UK, class and region are huge factors in when/how "love" is used--with the result that I'm now nervous about using it in fic, ever.

Actually "hon" as a generic term of address in the US is quite regional and class-based, too. It's mostly southeastern, as you said, and it's also pretty working-class.

Argh, why must language be so complicated?!