Hi Dalkey MC
I had found a number of references to the Commercial Hotel in the Irish Newspaper Archives but it was listed in all cases without a street address so I knew it had to have been in a prominent position. I visited the Dun Laoghaire local library today and thanks to Vintage1’s 'intensive enquiries'

my search was made much easier as I immediately started with Georges Street in Thom’s Directory for that year and I found the hotel with ease.
The full title and address was:
Ryan’s Commercial Hotel
56, Upr. Georges Street
Dun Laoghaire.
I am not sure how familiar you are with the area but the hotel was situated down near the People’s Park opposite two pubs which are still in existence Walters and The Cosy.
Looking at the photo the numbers run from RIGHT to LEFT, the shop front has obviously changed but the windows on the first floor would show, I imagine, that No 56 was the first two windows from the right.

I checked a number of Directories for Tyrrell’s Lane / Cottages without success but will keep trying.
John.