Extending Driveway

I'm extending my driveway to gain a couple of additional parking spaces but need some clarification on bed thicknesses etc. The current drive is crazy paved but the 5m x 5m extension is just going to be concrete (at least for the immediate future) It's only going to be used for parking a Spitfire or Yaris, both light cars so questions are

1. Do I really need to put down a hardcore layer

1. If I do what depth does it need to be

2. What depth concrete do I need and what mix

I have has a look at Cormaic's site, but as this is going to be a very lightly used area of drive I thought something a little less industrial might be adequate ?

Thanks

Jim