Solved....
I am deeply grateful to CaroleW, Cell, Peter V Crabb, Ray and Bessant for taking the trouble to answer.
Each of you, in quite separate ways, has contributed to solving my query. Cell's assumptions, without ever having seen the particular entry I was researching, were exactly right. The "Llannorgansh, Aberdare", despite being so clearly written, is actually "Glamorgansh, Aberdare". And to Ray - the fact that 1 Thomas Street was once an Inn as well as a grocer shop is relevant to my research. Thank you again to those who took the trouble to answer. Your efforts have enabled me to close this query.