Just looking at the 1:500 scale 1878 OS map, I think this is Nr 47-50 St Clare Street; Pendarves Row was up behind Union Terrace. My great grandmother lived in Nr 49 St Clare Street.
whitegirl, I have posted a picture of Pendarves Row. Don't know if this link will work
http://picturepenzance.co.uk/gallery/showphoto.php?photo=7583
If not, look in my 'Old Penzance Scenes album.