Done 5 or 6 days in the Megane RS rented from RSR Nurbug (
https://rsrnurburg.com/).
I highly recommend RSR. They have a huge range of cars, they can usually give you instruction, they have great support, and their prices are...reasonable.
Note that you are responsible for damage to RSR's vehicle up to an agreed limit as well as damage to the track (they will charge you for Armco repair by the meter), but I believe they will cover you up to I think 2M Euro for injuries caused to others.