Looking for Harriott of Coleraine Ireland

John Harriott and wife Mary (?) - a real brick wall. They had a son William Thomas Harriott (1816-1851) married to Grace McHenry (1817-1891). I am looking for any info on John Harriott and his wife Mary. They are on record as being from Coleraine, Ireland but I can find no information or trace of them in either Ireland or Scotland. John was recorded as being a gardener at the time his son immigrated to Australia in 1842.

The family settled in the Bungendore, Lake George and Goulburn area of New South Wales, Australia. They are also connected to the McFadzens.