yes there are two Nelson streets now though I think both were originally one - Great Nelson street runs from Prospect Hill up to Church street behind which was Shaws brow demolished many years ago for a car park which now too has been demolished. At uphill corner (rh as look at it from Prospect H.) is IoM bank then what was IoMSPCo offices then the back yard into what was Times Printing offices built c.1860's/70's (these fronted on Athol St to which Gt Nelson runs runs parallel) then rear of old Courthouse (built 1840) then road joins a T junction with Church St
On lh side is now an offshore bank building and in street yet more offices which took place of the houses I described.
Lower Nelson st is continuation of st across Prospect Hill running down into Strand street (coming out at rear of Marks & Spencers which occupies site of Victoria Inn etc) - there are still older buildings along both sides - those on rh looked at from Prospect Hill are a well known estate agents and it may be behind this in the area delineated by Prospect Hill and its leftwards continuation into Victoria Street that old property remains.