Yes, the Examiner and the Excello were one and the same. Be careful, however. There were at least two different Examiners and Excellos!
Your Examiner was renamed the Excello in January 1941.
Since you know your Dad's ship was torpedoed, I have a good idea which ship this was. If you'll send me your e-mail address (mine is "firstname.lastname@example.org") and I will send you a detailed list of the ports of call for this ship from May 1940 until she was sunk by U-181 on November 13, 1942.
Hope this helps you out!