thank you for your help and interest. It is much appreciated.
It is interesting that the NSW BDM have a Louisa Gibson, father William, Mother Mary A, death registered in Sydney in 1907. That threw me off the scent, particularly as there is also a Frank Gibson death registered in NSW in 1929, father Thomas, mother Isobella. Frank Montague Hillyard Gibson's parents were Thomas and Isabella.
However, I am inclined to go with your record in Richmond as Frank Montague Hillyard Gibson was being looked for by a firm of solicitors, stating that he was formerly of Richmond.
Many thanks, again.