Many thanks for the help and suggestions. I spent yesterday with the 1881 census and place names and think that I have traced the probable route of the ennumerator. (As an aside a sudden change in occupations from Miners and Farmers to Fishermen was also backed up by a check of the map) !

On my 1:25,000 map there is simply too much detail! Ironically on the less detailed 1:50,000 plain OS map, there is clearly a track leaving the Foxdale to Glenmaye road, just opposite the Arrasey Plantation. On this track there are three dwellings clearly shown, and the word Carnagrie - I assume that the middle one is the "Caryngreai No2" of the census.

Thank you again for the help, one more little piece of the jigsaw seems to fit. Now to trace the family......