Pickup car in Paris or Vernon

Not Vernon -- way too small. Pick up from Paris or some place like La Defense.

Always pick up at a place that has lots of cars -- not some little town. We usually pick up at train stations or airports. There is a small fee for that but we would prefer that to the experience when we picked up on the outskirts of Rome and they damaged the car driving it from the back to the front of the building and we had to either take a car that had been rammed into a pole with significant damage or not have a car as they had no other available. I would get your car at CDG or at an office in Paris -- La Defense might be a good choice.

One option is to rent a car on the day you are leaving Paris. I would NOT rent one in the city--get one either at CDG or perhaps the La Defense district. Otherwise you can use the train and bus to see Giverny and journey on to Rouen, and then rent your car in Rouen for the rest of the trip. A couple of things to remember about driving in France--your credit card may not work in the autoroute automated machines--even if it has a chip (which all Australian cards do), so use the cash lanes and have bills no bigger than 20 euros. Most of the cash machines also have a slot for credit cards, so you can try that first to see if if works for your card. Also, there are many speed cameras--don't risk going over the limit even if everyone else is. Lastly, being a Aussie, your credit card should work at automated petrol pumps, but sometimes these pumps reject any foreign credit card (I know from experience!). So don't let your tank get to empty before you try to fill up. I once had to go to three different petrol stations in Bayeux before I finally got fuel.

Rouen ought to have a good selection of cars, and you wouldn't need a car until you leave town. ("Ought to" means "in principle, since I've never picked up there.")