By the way my own (temporary) set-up for my Touran. It needs some refinement but works alright.
Basically two plywood boards which are attached to each other at the end of the day, both front seats have to be pushed forward as far as possible.
Leaves a space of 2 mtrs. Camping chairs, table and food in a box go below. Behind the seats I store the luggage and water.
Definitely cheaper than the set-up I could buy for this car.
Mic, out of curiosity. What did you do to secure the bikes at night?