Cotter Lane, Bantry 1849

My cousins ran a bakery for many years just off of Main st in Bantry. The lane behind the bakery was named after them & has a plaque to comemerate this, labelled 1849-1968. I am interested in the earlier date. Have found a reference in Slaters 1854 to Denis Cotter baker of Main st, which may be the same business, but for this early stage I'd hope for William (father of Denis, who ran it, but was born in 1872). A member of this family (not responsive to my requests) is a local historian & I believe obtained the 1849 date from a record. Where should I look for a record to back up this date?? ..Cheers from Chay