[joglynne]

The place where the wires seem to be most in danger of breaking appears to be where they are constricted by the right angle bend just before the wall plate. As the sconces will not have been made in one piece have you checked to make sure that they do not unscrew at this T junction. If you are lucky and they do then you will have more of a chance of drawing the old wire out and with luck can use a draw-thread to feed the new wire through.