Hmm the Z for 16999 you sure its not a Jap spec, or a dodgy scam name next to the advert.
When it comes to selling your car 18900 you should easily get IMO, put it up for 19300 and expect to be haggled down. It all depends how you advertise it and what words you use. Remember when you are selling a car, people are always dubious, its human nature to question okay why is he selling and two whats really wrong with the car.
My advice is when selling be REALLY honest in the advert. You have to gain peoples trust to be interested. Let them know it was your pride and joy, take good detailed pictures of it, including under the bonnet, if slight curbed wheel dont be afraid to show, it tells people you are being honest. Let them know how well you look after it ( you could slightly blag this part ) then Im sure you wont have a problem mate. Its as good as sold. Cos its convertable, try and get into the mind of the kind of buyer who would want to buy it and then list evcerything that kind of buyer would want to know