I have an old map of St Ives and there is a road called Back Road west... I cant see a Back Street . I can send you the map.
Before tourism got there most of the streets of St Ives old town where were poor folk lived, it was a fairly poor town as it was dependent of mainly fishing. Rich folk lived up the hill!
Back Road is on the route you'd walk to Porthmeor beach, close by where Tate St Ives is.