@Darwin I would have said that if you hadn’t said it already. I’ll address another question that was raised above, about why people try to imitate the accents of others.
I find that when I go to another part of the country, say Southern Ohio, or North Carolina, I quickly find my accent changing. If I’m there for more that a few days, I’ve almost completely changed. This change happens without me willing it, and sometimes I get self-consious about it, feeling like a poseur or something.
Just as the attraction to difference is good for the gene pool, which helps survival of the species, so is melting into a new culture helpful for survival of the individual. Once you’ve been married in, so to speak, you need to take up the culture of where you are, or people, eventually, will find you disrespectful. This is why Americans hate the idea of foreigners who don’t speak English. They think it is disrespectful.
So, when you are at a bar, and you find yourself imitating the Aussie or the Brit, they are probably doing a similar thing, as you try to arrive at a mutual accent somewhere in between.