In America, Ex and Former has different meanings.
“The label “ex” (e.g. ex-Coastie) should lead one to believe that this person was once a Coastie but it no longer because they were discharged for wrongdoing or some other ill thing (actual title: Ex-Coastie commits wire-fraud). Whereas the label of “former” spells out that the individual was once a member of said service and left on good terms (good conduct discharge, retired. etc.).”