As of 2016, the ACO have improved the online access to race tickets, including camping. We tried this last year and saved about £200 on fees and such like cherged by race ticket and travel websites. You can even print e-tickets, and get them immediately, if you're running late on the organisation front.

Here's the link to the ticket website for 2017 (also in English): http://ticket.lemans.org/mes-dates-billets-dentree-auto