Why can you not get a test drive? Do they not think you are serious or something? Some tips may be forthcoming on this one, but my tips for test drives:
1. Ring and book first - makes you look serious and organised
2. Collect some material together - model brochures etc. - and put them in a file. Take them with you on every test drive. It's a gimmick but, again, makes you look serious
3. Turn up well turned out. It's like going to court - the smarter the better!
At the end of the day, they must have dozens of people chancing their arm on a test drive every week. You just need to convince them that you are really up for it
If the problem is that you can't get to a dealer to organise a test drive, give the nearest one a ring - I've known people have the dealer come to them for a test drive. They normally only do this to your work's address, of course, but it's worth a try...