I'm an American who lives in Germany and hear many kinds of English spoken by many nationalities.
Just as "one can either write
organisation but the main point is to be consistent" I have also generally applied this rule to my speech.
Especially when I was teaching English I would make it a point to not say phrases such as:
even though I thought it was cool. And instead of saying:
Shall we go?
I would say:
Do you want to go?
I can imagine if you are teaching English or if you are representing a company from London or New York or Sydney you have a certain obligation to speak as if you come from that place.
In what contexts is it important to maintain your accent or dialect?