Once again, I look forward to hearing other people's thoughts!
How would G be able to tell that the site is UK based, and a UK resource?
From your .co.uk domain. But if you have a UK-based site that has a .com domain and is hosted in the US, you would do well to get ranked in a UK pages search. Further, some folks believe that even if you have the correct country specific domain for your location, it still helps to also have hosting in your country too. Certainly some of the SERPs I follow here in Ireland would tend to support this.
Note - this issue has been discussed many times in the UK and Ireland Search Engines [webmasterworld.com] forum. You may have better luck posting there.
They are all on first page of serps in all SE's for their targetted keywords and phrases whether the search is done from the USA , France ,Oz
The question is not just about where the search is done from, it specifically referred to when the searcher selects the "pages from [regional Google country]" option. Are your US-hosted pages still top when a searcher in Oz selects "pages from Australia"?
Can't speak about France, but certainly the UK experience seems to support what you call an 'Internet myth':
why am i on the .com search engine but not on .co.uk [webmasterworld.com]
Getting a UK site listed in UK searches [webmasterworld.com]