i have a friend who trades zeds among other sports cars and he does it on a per car basis, their cut that is, if its been sat on the forecourt costing them money he has occasionally let it go for a v small margin just to free up the space for the next thing he thinks he can sell...
I would keep an eye out and see how long they have had said zed, if its been there a few weeks then there are more likely to try their luck, if its been there for 6 weeks plus then they might be more willing to take less margin, just be prepared to walk away from the deal, and try and have a few examples in mind...
also, be warned that if you test drive one you may turn into a teenage kid again