Seeking Patrick Darby c 1806 (also posted in Co. Wicklow)

Hi there, 

First time posting here - I have hit a brick wall with my paternal line and am seeking some asistance please.

My 4th g g father Patrick DARBY (b. circa 1806) emigrated to Australia with his Wife Amelia/Emily/Emilia Lac(E)y in 1854 with their 3 adult children. Thomas & Patrick were aboard the Sultana with their parents from Liverpool to Portland, and Jane (who was with her husband and 2 small children were aboard the Almora). The children were all born in Blanchardstown, Dublin - as were the two granchildren, there is mention of Mulhuddart in one certificate and I have what I think is a firm record of residence in Coolmine, Dublin from the valuation records of a dwelling lease from a Thomas Lacy. Death records here in Australia suggest his wife was from Co Dublin so this could be a relative? As these areas are all within close proximity, this all seems to fit.

However...Patrick's death record says that he was born in Co.Wicklow and despite my best efforts, I cannot find hide nor hare of any record of him in WIcklow, nor anything further in Co Dublin, such as a marriage. Darby does not appear to be a common name in either county.

I have begun trawling through the images of the catholic parish registers as our surname has been spelled/transcribed many different ways over time and the online indexes have proved fruitless, but wondered if anyone had any advice on how to limit my searching to be more effective. 

Many thanks,

Caz