I was going to suggest as Alan did, go when your contractions become regular or if your waters break - they shouldn't send you home until you are further along seeing that you live so far away.

If you don't think you are going to make it, call an ambulance, they have everything that will be needed to deliver your baby and that is what they are trained to do.

Definitely would pay to have a pile of old towels in the car - if you do feel that you will be delivering in the car, try to get these towels (probably a job for you DH) under you and around, that way they can be thrown out - much cheaper than the car (very hard to get that smell and mess out of your car).

Good luck with it all.