After being let down by Sicily By Car (they would not accept a payment with debit card, even if I had paid the deposit online, then refused to serve me all together because I complained about it…) I went to Sixt! They were absolutely fantastic… In five minutes I had a vehicle! The gentleman that served me was kind, professional, and explained everything so well. They accepted Debit Card payment. Keep in mind they will take a deposit of about £250 that will be returned when you bring the vehicle back. They were not on the desk upon my return, but you can conveniently drop the keys off in one of their special drawers. I was a little anxious about the deposit for a few days, but I have been reassured by the call centre that it will be retuned within maximum 10 working days.
The vehicles are kept on the first floor of the car park. You will be given a ticket to exit the car park.
The only downside is to know where to drop off your car (if you are renting a van). I parked up the road opposite to the airport. They have free 60 minutes parking and free 90 minutes parking. For longer time you will need to use the other paying car parks, there are several but the ones opposite to the airport should be cheaper.