Applying a checker material to the model displays clearly how quadrants will be treated once the skin is applied. Areas that are too stretched needed working on.
I used the UVW Unwrap tool to take the quadrants of the head and lay them out flat so segments of the original photo to be cut out and repositioned on a flat map. Some areas of the map needed to be altered as they were cluttered or overlapping. So I used the relaxed tool to move them in suitable positions.