By default, the Google search page is displayed in the language from the country you're in. You can change this in the 'preferences' on the Google page. The actual text near the language preference is:
Display Google tips and messages in: [<LANGUAGE>]
According to me that's only interface related and (at most) tips/local event related (like Queen's Day etc.). But it also influences the search results. Just try it by switching to several different languages.
Shouldn't search results be the same?