There are a lot of more recent problems with car rental people mainly because there is much more demand now so they are starting to add all sorts of charges, even now with the full to empty fuel policy and refunds if you return the car full they have added an admin fee, both Goldcar and Firefly for example are charging €20 plus IVA, Europcar Interent €27 plis 21% IVA, but they cliam that it is for your convience
If they take a deposit for fuel and other risk there ios no set time for the refund but when I have querued this with a credit card company they say that 10 days is reasonable and that they will become involved if you ask, even arrange a charge back if the car rental compnay doesn't respond
If like me where I have an insurance policy to cover any excess, they take a large deposit, between €800 - €1200 but they don't make the charge just block the amount
Regardless of companyI always insist that when I return the car that they come and check the vehicle