Flew there for about five years on the trot for the 24 Heures...a good crack, but getting expensive (last time was 2 years ago). The cheapest part of the trip is the entrance to the circuit...about £40 for three days.
We used to arrive on Friday afternoon so as to:
a) fly the track
b) get into the pits, which are open to the great unwashed until 6pm local time Friday.
A slot number (and time) is a must, although there was never any problem either getting one or changing it if circumstances dictate, or even arriving early. The GA parking is pretty much empty now compared with a few decades ago. Arriving in the vicinity, they are usually very accommodating if you ask to fly the circuit, certainly on the Friday. Fuel up on arrival if you need it. The bowser comes to you if you ask over the radio.
The AIC should be out soon, available from the French website
http://www.sia.aviation-civile.gouv.fr/ or thereabouts. This also has a phone number for PPR & slot times.
Landing / parking was about £55 for a light two-seater for the three or four days.
Camping is available next to the tower (no pre-booking required), but not under the wing. The airport offer a little charabanc (navette) service from the terminal building to the race entrance for a few bob. We used to pre-arrange car hire, which they delivered to the airport, so as to get out for a decent meal. But it was no good for getting across the airfield to the track. The track entrance is about a mile or so walk from the airport terminal. The garage at the airport entrance do reasonable nosh, and have showers!
The Chinese restaurant on the Mulsanne straight was surrounded by plastic sheeting last time I went, so you don't even get to see the 200mph+ cars whizzing by any more. You could still eat there, however.
We always either stayed an extra day, or flew out 2 hours before the foregone conclusion race end, so as to avoid the rush for departures.
They got rid of the
art-deco terminal building several years ago, now replaced by some glass-and-concrete monstrosity.
Hope this helps. Now tell me you aren't going for the H24?