A couple of things you should know when renting with Masterkings (i did via Zest Car Rental).

1. Their cars are older, expect 50k + mileage
2. A deposit was taken of 25 euros for the toll transponder which I assured them I don't need. I was promised it would be refunded back when I returned the car. Their Ts & Cs state 21 days. I have just been on the phone to Zest to try and understand why after 35 days I haven't received the money back.
3. my flight landed at 18:20 and I made my way to the little cabin at the other end of the airport car park (it might tell you it's 'on airport but only just) - expect a long walk from arrivals through to the back of the car park. After queuing and witting for my turn the clock ticked past 20:00 - I was charged 30 euros for late pick-up. This is unacceptable - I queued and waited- it took them 20 minutes to do the paperwork. So, got their on time, waited for my turn, and was charged for the privilege.

After the charges, they aren't the cheapest any more/ If you want to avoid charges and go to an airport desk to do the paperwork - collect the keys etc this isn't the one for you.