I don't know the answer to this one, but a few years ago the car hire firms wanted to be paid in cash and had to be persuaded to take a credit card! However, credit cards are now the norm and with the advent of the motorway tolls many firms keep your card details in order to pay your toll fees after you've left. I would suggest you contact http://www.economycarhire.com and ask them the question. When you rent through them, they take your money when you book, so I assume you could send them a cheque or pay by debit card.