When using the SP Search Centre and looking up people, SP is returning results that I am not expecting. If I search location x it returns all the people that are in that location but at the end of the results is a person that should be there and there location is a different one. I cannot see where it is referencing location x to this user. How can I check/see why this person is being returned?
You can not. There is no way to tell why or why not SharePoint search retuns it's results.
If you are you searaching in a single property like
location:somewhere SharePoint will return only results with the given value in the given property. (Unless the property has been changed lately and not been crawled since.)