The "correct" way to do this would be to look at what the browser sends as the preferred language. Unfortunately many people set it incorrectly.
I am not sure that geoip is wrong in this context though - a Brit in the US is likely to get American puzzles.
You should probably use British English for South Asia and some of the other Commonwealth countries - I do not know about Canada and Australia.
I remember reading that schools in New Zealand now use US spelling because it was too difficult for people to figure out how to change settings in MS Word, but older people probably use British spellings.
Comment
The "correct" way to do this would be to look at what the browser sends as the preferred language. Unfortunately many people set it incorrectly.
I am not sure that geoip is wrong in this context though - a Brit in the US is likely to get American puzzles.
You should probably use British English for South Asia and some of the other Commonwealth countries - I do not know about Canada and Australia.
I remember reading that schools in New Zealand now use US spelling because it was too difficult for people to figure out how to change settings in MS Word, but older people probably use British spellings.