Kosta ,
I think you will find it difficult to find one that will allow you to ferry a car. I have been dealing with them for many years, I rent a car for the whole time I spent in Greece (4-8 weeks, almost every year) and they look after me, that's the reason I still use them. I book a few weeks before I land in Greece, I don't pay a deposit and I pay them the full amount at the airport when I leave. They know I want a late model car, one with non Chinese tyres and low km. I always look after their cars but I use them, I do a lot of k's and give them back clean and undamaged.
I have a personal relationship with them, I haven't been out of Australia for two years and they keep in tough with me via email around May asking if I will be going there, hopefully next year.
Not sure if they will allow a new customer to take a car on a ferry.
They will not allow me to take their car out of the country.