I am not sure if you have researched further back but in the booklet I have on the NZ Dignans it says the Dignans came originally from France.
They were a family of substance in Normandy name was D'gnan, but also owned land on the Spanish-French border. Connected by marriage to the D'alveraz family. Operated as wine and spirits merchants, owned trading ships and had considerable investments in England and properties in Ireland.
French Revolution time the mothers to be and children were sent to Ireland so the sons would be born on Irish Soil.
Later family connections to Thomas Cook and Sons not sure if banking or travel side.
Finally the whole family fled France to Ireland.
Left for England as Catholic Church joining was compulsory or your land was confiscated.
The children of the D'gnan family were educated in England and later France. This was the time of name change.
While in Ireland Peter Dignan of Loughrea married Margaret Lynch of county Galway.
One of her ancestors was Judge Lynch and Charles Lynch the planter of Virginia who instituted Lynch Law.
Peter and Margaret Dignan had eight children.
Bridget married and sailed for America,
Mary married Mr Hobbs and stayed in Ireland.
Peter and Patrick went to England then Australia. Patrick continued to NZ.
The rest of the book is about the NZ branch.
There is a sketchy and undated family tree .
The tree is from Peter and Margaret and another tree of Richard Derron and Mary Windyer. Derron being NZ Patrick wife's maiden name.
They had Ten boys and one girl who died.
I advertised the book on the NZSG forum as it only cost me $3 but no one as yet has replied.
It is only a thin A5 size soft cover booklet called, 'Te Ana Rangi' by Audrey Drummond. I looked on the Family history shelf of The NZSG Library and there is no book there on Dignan's.
It may be that someone took the booklet further and made a proper book about the family so it might pay to check Google. The NZ family lived in the mount Eden area of Auckland.
Regards
Elizabeth
O