Trying to find something on Margaret McCana. This spelling is taken for the churchy registery entery for her marriage to Patrick O'Brien. The marriage took place at St Patricks Chaprl in the Westy Derby area of Liverpool on August 27, 1843. From research the name might have been McCana or McKenna. The registery lists her father as Toal McCana. It has been suggested that that was short for Tuathal McCana.
The English 1871 census has her in the West Derby area of Liverpool with her family. It lists her as 48 which goes along with the 1851 and 1861 census's, they have her as 28 and 38. The 1871 census lists her birthplace as Delfast which I take as just a transcription error.
Running into a brickwall on tryin to take either Margaret or Toal back any further in England and Ireland.