Thank you for the look up Mike & the picture, Rupert. I had not given thought to the possibility of the 1841 Milners living in a boarding house. The only early map I can find showing building footprints does suggest that in 1838 there were indeed L shaped properties, but of course we cannot determine whether the extra at the back were wash houses etc.
If I do buy new tree software through Amazon & get a 6 month access to Ancestry one solution would be to look up the 1841 neighbours of George & Ann Milner to see if they lived in a guest house or if a close neighbour was the guesthouse proprieter.
It looks to me, Rupert, that the grand buildings behind the fountain in your picture were not too dissimilar to those properties which stood further down Paradise St, though do correct me if you disagree.
Again, thank you both.
Shirley