Also, the car they rented does not have an enclosed trunk like we are accustomed to here in the US. If I were going to transport a body around, I would try to get a car with a real trunk, assuming that they are available in Europe.
They are available, but hatchbacks are quite common and you wouldn't want the sales staff remembering that you insisted on paying more if need be for a larger model with an enclosed trunk.
The Renault Scenic does have a built-in partition that you can snap in place over the trunk space - to prevent smash-and-grabbers from seeing what you have in your trunk.