Refence Webb's lounge, to which Frances refers. 20 years ago I gave to Manx Museum a piece of shopfront for Webbs Lounge, which I had in my cellar. It was a carved piece of wood which was one of the two window sills, and would, I recall, have been covered with glass. I can remember other shops having sills of similar type.
The Douglas Corporation had a picture of Webbs lounge, with this sill (That is how I knew it was a sill) on its website some time ago. It is not on their site now. It was a picture which was part of the centenary celebrations. This picture would give a flavour of the street.
You may possibly get some feed back from Douglas Corporation, or maybe they borrowed the picture from the Manx Museum?