Aranging car road tests

Lo all,

Ive recently been offered a job to write small articles for a motoring website. Part of this includes writing road tests for cars. As this is my first foray into such things, I haven't the foggiest of how to go about requesting cars from manufacturers press fleets and such. Do I need to have some sort of press ID or something? I'm going to talk to both the company that im writing for as well as doing some ringing around car companies on Monday but just wondered if any of you lot had any experience in this kind of thing?

Cheers,
DJ