1) What programming language would you like the script to written in?
PHP and SQL are fine.

2) What operating system will the script reside on?
Any at all.

3) What kind of budget do you have?
0 personally, but if I have to pay, my client would be forking out the bill.

4) Does it have to be open source? Or can it be proprietary?
Open source - I plan on using it only as a base script.

5) Can the source be encrypted?

6) What features are you specifically looking for?
~ An editable list of makes of cars, and style of cars.
~ Easily to edit information
~ A picture gallery for each vehicle
~ An enquiry form, linked to a central database

7) Do you see any working examples of the script? Show us.
http://www.flexxilease.co.uk - The best