Thanks to all for your constructive replies. Though I am tempted to sell up (and did call the dealer this morning to mention it to him - though he was out), I genuinely want to grow to love the 350Z. I like the car's looks and it's sound system but, as yet, little else.
Yes, I did test drive the car but there is a BIG difference between going for a fifteen minute test drive (at rush hour) and using the car regularly. I guarantee I WON'T get back pain after a fifteen minute spin in a car. It's the 30 min-1 hour or more drives to and from work (every day) that triggers this.
I said in my post that I can live with most of the 'faults'/'quibbles' that I have but the one that I really can't live with is back, shoulder and neck ache that gives me a groggy head.
So any further comments on this would be much appreciated.
PS - I knew that I was walking into a lion's den posting negative comments about the 350Z on an owner's board but I am pleased with the responses so far and welcome others.
PPS - to answer an earlier reply, my previous car was a Golf GTI 1.8T imported by motorpoint and, for half the price I paid for the Z, looking better value by the minute.
Thanks again
Jon