I used to know a chap that marshalled at Le Mans. The Brits had a post towards the end of the Mulsanne, near the golf course.
I recall that a couple of years ago, there was a big shake up with the LM marshals, but I think this was just a French thing, rather than the British courses/training/grading system, which I assume you've progressed through.
Contact the marshals clubs CLK has mentioned, ASAP.