This is a niche market with a handful of fussy buyers. Not everyone has a spare £18k or so. All the cars are desirable to different people.
The younger crowd may prefer a 430 for modern looks.The old school will like generally like a 360 or a 355 for its classic looks.
It does really depend on how you market your car, how desperate you are, and the actual build and detailing of the car, as these buyers will view a few.
I have friends in the used car trade and they are struggling selling second hand cars due to the economical climate, so we are going to find it extremely hard to sell ours.
Just about waiting for that right buyer to come along, it will take a long time unless you are desperate and want it to go for a ridiculous price.
The shows are coming up, try and attend all of them, you might find a buyer there. Best of luck with your sale.