Purchase advice for frequent drivers

Good morning, I am looking for a cheap car for many drivers (about 300km/day) it should consume little, be reliable and of course cheap in maintenance… so I look like so many, the perfect car Our budget is 6000-7000 euro, we already have a car (Opel Meriva on LPG) and the new one would then second car or other around… depending on. After fuel monitor and forum I have two in the narrow selection, VW Fox and Citroen C1. Everything is not very comfortable, but rather useful minimalists, but that’s ok (so a pendulum egg is not made for 10 years…at least I don’t want to do that forever). Price/performance is with both similarly searching through the usual sales portals, whereby the C1 seems to be lower in consumption, even in maintenance the Fox is probably a more expensive fun. Still missing the reliability of a 3-4 year old car with about 40000 km down. Can you help me there again? Which repairs can be made? What is to be paid attention to? Our Opel keeps still the 5 years old car is well repaired and still very good for you said to me.