Interesting - the VX production's only similarity to the concept is the exterior shell (although the production model is slightly larger) - everything else and I do mean everything, was scrapped for current production parts - the interior, engine, drive train, wheels and tires - the only thing that bears any resemblence to the prototype is the body styling (general shape and tire mounted in the rear door - even the door configuration was changed from flip-top/side-opening-door to side-opening-door only). I could imagine that Simon would get upset at what was changed.
Looking at some other references - it appears that it's mostly in the Brit magazines that Simon is named as the designer - even in the non-Brit references above they either mention him as part of the team or use the term "penned" meaning that Cox did the concept sketches - so from that aspect he should be given credit for the VX. In the Japanese publications they only mention him as part of the team - the reference to his interior design is in one magazine I have that shows the original prototype "binnacle" dash design, attributed to him by name. I'll take back my earlier statement as I now believe it's incorrect and that Simon should be given his due as the designer since it appears he did the original concept sketches for the exterior as well.
I've got one other reference if I can find it that has an extensive interview with Cox and boss - I'll post an exerpt when I can figure out what I've done with it.
-- John