Might be safest to ASSUME you're dealing with the home team, you should be able to pick up on UK and/or Antipodean nuances pretty quickly, assuming there's no mention or suggestion of locality/nationality in the poster's profile. Some posts will make it obvious, e.g a tour of the Ozarks/Lake District/Bush, etc... Also color versus colour, pictures showing different suburban architecture, yellow rear number plates versus white license plates, you get the idea.
A.