Hi Ian,
I have found a little information. Sena Garrett's real name was Charlotte Senar Garrett born in 1884 and she was the daughter of Robert Garrett and Isabella Kaneen. I think Charlotte or Sena married a Richmond. They had a son named Robin. I know he was born sometime after 1904. We made a trip to the Isle of Man in the 1970's and met with Robin but did not keep in touch with him or his family. I believe Robin drove shuttles to the airport. Any information would be greatly appreciated.