Traveling to Greece (Athens)

I will have a road trip to Greece with few of my friends and since we will not book an advance a place to stay, because we do not really know where we are going to stop and how many days we will stay in a place, because it is an unplanned trip. Therefore we need to find accommodation on spot, so i need a site in English other then booking.com on which i can find small villas or hotels with owners phone number if possible. Thank you!