McManamon/McMahon Family

[Corky44]

Would be grateful if anyone has any knowledge of this family and why they changed their surname.

Patrick McManamon came over to England as a result of the potato famine in Ireland.  Patrick and his wife Bridget both worked in the Cotton Mill in Preston. Between 1864 and 1868 they had 3 children, Thomas, Ann and Bryan. In the 1871 census it shows the family living at an address in School Yard in Preston. I believe the family left the Preston area in 1871 or 1872 and moved back to Ireland. Bryan the son returned to Preston in the early 1890`s. He married Mary McKeown and they lived in Preston until 1913. After this date the family moved to the Southport and Liverpool area. For some reason the surname changed when Bryan returned from Ireland to Preston from McManamon to McMahon.
My great grandfather Bryan used to tell family members that the family had links with Cork.  Any help would be much appreciated.