Informal way to address a woman (who you do not know) in the UK?

When addressing a man informally I tend to use "mate" or "my friend" however it has never been clear to me how to address a woman. In London, where I live "dear", "luv" or "darlin" seem to be used frequently but I am not a fan of any of them. I therefore don’t use any term unless I happen to know the woman’s name.

I quite like the way "lady" is used in the US so perhaps that is an option.

Any suggestions and what terms do you use(if any)?