I forget which campsite is open, but it isn't Maison Blanche. The weekend goes from Saturday to Sunday (don't they all?). IIRC there is some kind of scrutineering during Saturday then testing on Sunday. This year it isn't pre-qualifying. Mr McNish told me that he won't be at pre-q even though he is driving in the main event.
It's a great time to be at the track as you can really get around easily - you can take the car in for maybe €9 (or was it €15?) and drive to those parts you can't usually be arsed to walk to. OK, the cars aren't quite racing, but they are going pretty quick and with a much lesser crowd there are some good photo opprtunities, if that's your bag.
It is also much freer getting around in the pit area and paddock - little security, and important people have more time for you and seem soooo accessible. Many of the concessions are open so you can get sustenance.
Highly recommended!