Thank you for your excellent 'state of play to date' summary PJ, and thank you all gentlemen for your other exotic suggestions. Sadly it is none of those though.
As PJ has correctly highlighted, so far the closest answers have been that this was designed for specific markets, usually based by the sea.
I fear this puzzle may still be here for another 12 months, so to help get it solved, a clue to consider is markets where Vauxhall Viva-based vehicles have been built and sold (and I don't mean the UK!).
The reward for the correct name of this Vauxhall is now increasing to 2 points as an added incentive!