Murphy - Place of Birth

I am having great difficulty in trying to establish where my grandfather was born. 

His name: Charles Murphy, Born 25th September 1872.
His wife: Elizabeth Fardy, Born 22 September 1869

They were married at Rathgar Rd Church, Dublin 21st February 1897

Charles worked in Guinness. I got his date of birth from their records. The archivist there said that Guiness would not employ a person unless a birth or baptismal cert was produced. A handwritten note on Charles personal file cover looks like "handed baptismal certified 20/8/26".

Charles parents(Daniel lived at Batt St, Wexford, Elizabeth lived at Castle St, Wexford) were married in Wexford 1865.
On the 1901 and 1911 Census and living in Dublin, Charles declares he and wife were born in "Co. Wexford", all children born in Dublin.

They seem to have moved to Wales as they had a son, Peter, born in Neath 24th July 1867.
They then had another son Dennis, but he was born in Wexford 12th february 1870.
Then Charles was born in 1872, BUT where?

I've checked state and church records without success. 

Any advice on another path to follow in tracing where Charles was born?