I appreciate that car hire horror stories abound, but feel it only fair to give credit where it's due, especially as Athens airport is so significant for people going to Leonidio.
Just had a good experience with Goldcar. Low price basic hire with unlimited mileage, received an upgrade and collection and return of vehicle both efficient and hassle free. Large amounts blocked on credit card but significantly no compulsory fuel service charge if full to full on return, unlike with some companies where I have had to pay around an extra 40 euros in the past. Potential bodywork damage was clearly explained as being only anything over 3 finger width size. I did find the counter staff quite aggressive about pushing extra insurance premiums, but felt confident about resisting this as I have a separate annual cover for my excess.
The shuttle bus is easy to locate at the airport as is the depot from the motorway. Fuel can be purchased from motorway services just a few km before the exit junction.
