After many years of searching I have finally found church two records, a marriage in 1877 in Mullingar and a birth in 1879 in Dublin. I availed of the Findmypast 'free' weekend just past and there they were. All other record details tie in such as subsequent children/deaths on the civil register and the censuses.
These two events are just not on the civil register. Who was responsible for registering a marriage in 1879? is this a common occurrence? Obviously some fee was payable and in the case of death a doctor's cert perhaps, but I dont think poverty was an excuse in these cases.