1. Which location would you recommend and why?
2. How quickly can immigration to these locations take?
3. Which has the best quality of life, both now and over time?
4. Is the work ethic similar to that of London, more intense, unknown?
5. Any tid-bits of advise?
Immigrating to the US is easy if you have an employer lined up, however getting a green card or full citizenship can take awhile (5 years?)
In the US you will absolutely need employment for health insurance. Don't get sick while unemployed, or you will have to move to Australia anyway to avoid the bill collectors :-)
If you plan to stay in a city, London, San Francisco/LA, Sydney, etc. all have high costs of living.
I am from the US, I wouldn't want to live anywhere else permanently.
But if I were an immigrant, particularly from UK/Europe, I would have to have a very specific reason to move to the US.
If I wanted to start a business, live in a suburb, own a gun, lower taxation, etc. the US is great. Though you will only find lower taxation outside of NYC/Boston/Chicago/San Franscisco/LA/Seattle, etc. Diverse climate and people.
Quality of life is very subjective. If you plan to live here through retirement to death, the US is a terrible place to retire with low social security payouts. You would need to move to low cost area, unless you can afford a nice condo in Florida. If you plan to stay in a city unto death, make sure you find a rent controlled place...
Australia is probably a better fit if you don't care about any of the above, but we would welcome you here regardless.
If you are more interested in exploring the East, then Australia is the obvious choice. If you want to be able to explore Central/South America, and get back to London relatively quickly then the US might be better.