You need a Credit Card and driving licence.
Some suppliers accept Debit Cards. The card must have a MasterCard or VISA logo and your name embossed (raised) on the front. It cannot be a pre-paid card. There are two ways, to view which supplier accepts Debit Cards (1) Next to each car photo is a link entitled IMPORTANT INFORMATION, click this link to view conditions. Try a few different suppliers as they do vary. CASH is not accepted: (2) On the search results page (where the available car photos are displayed), down the left-hand side menu at the bottom you may see a tick box, to filter out suppliers who do not accept Debit.