This is interesting. I haven't seen this Vignale prototype before, and at first sight it looks very similar to the production Vauxhall Viva HA. But there are a lot of differences. The profiles of the bonnet and boot (hood and trunk) are different. The bonnet on the production HA is more horizontal, with a pronounced step down to the front grille, and the boot has slight fins at the edges. The Vignale version smooths out these features. The profile of the top of the grille is similar on both models, but the bottom of the Vignale model is more curved. The front bumper is different, with the side/indicator lights as small pods mounted above it. The rear bumper also wraps around much more than the production model. The rear lamps are also quite different.
Along the side, the trim strip is moved down, with side repeater lamps at the front, and the fuel filler has been moved further back behind a flap. The rear windows are also different. The Vignale ones appear to have a metal frame, while the standard ones have the hinges bolted through the glass.
Overall the changes are quite subtle, but I think it changes a rather dumpy, uninspiring looking car into something with a distinct hint of elegance about it. I quite like it.