wriannam

I have not found any mention of Kent Cottage in Dalkey, but there was a Kent Terrace, which could be related. The Terrace is listed separately in Thom's 1848 and appears to consist of 4 or 5 houses in a terrace, plus cottages to the west later shown as Barnhill Villas on maps - the terrace and villas later became part of Barnhill Road.  The 25 inch OSI shows Kent Terrace on the south side of Barhill Road at the junction of Dalkey Avenue.

If you look at these houses on Google Street View you can see a plaque on the western end of the terace reading 'Kent Terrace 1836'

Dont know how this fits in with your Christopher Coghlan... cross-checking census returns and deaths I found a death cert for a Rosanna Cox on the 27th June 1901 at Kent Cottage, Dalkey, and the same person on the 1901 census earlier the same year with her husband and family - the household is listed as Barnhill Road (part of), Dalkey Electoral District. (The "part of" notation usually means that remaining houses on the street are listed under a different electoral district.)

I dont see any Coghlan/Coughlan's on the street in 1901 - have you found your Christopher on the 1901 and/or 1911 census ?