Another longshot in case anyone looking for Guinan or variation can match to the following.
I possibly have a Guinane in my ancestry. I am from Bridget O'Brien born 1835 Ballywilliam /Castletownarra near Nenagh in Tipperary. Her parents James O'Brien and Mary Maher/Meagher married in 1828 registered in Templemore parish or diocese and they were from Thurles (James) and Clonmore (Mary). A possible baptism for my Mary Maher is 9 Aug 1810 - Parish/District Templemore, address Borrisberg which is between Templemore and Clonmore, RC, parents John Maher and Judith Guinane, sponsors John Meagher and Nancy Mackey.
Deirdre's Guinan's were at Roscrea about 17kms north of Clonmore where Mary Maher with mother Judith Guinane was from. Mary was born about 1810 so her mother Judith Guinane may have been born about 1780-1790 and could be a sibling of Deirdre's James Guinan b Roscrea, Tipperary 1795.
I only have FMP to look up and looking under Guinan and variations 1790+/- 10 there seem to be a couple of Guinan/Guinea/Guynan families in Cashel and Emly and others in other locations in the south of Tipperary as is Cashel. There are a lot from Killenaule in south Tipperary.
No results for Roscrea in that time frame,
FMP shows Honora 6 Oct 1830 and Mary 20 Oct 1827 bapt to David Moylan and Mary - Guinan for Honora and Guman for Mary - at Cashel and Emly.
Marilyn Long
Australia