ian,
No discounts offered to clubs.
The only way to save is to purchase an advance day ticket at €14, rather than “at the door”. Alternately, if you can persuade 9 other like minded souls, entry is €12 each for a group of 10.
Having attended since 2008, I’m giving it a miss for a bit.
I see that there are still some £34.50 singles from London to Paris and Paris to London available, so if you are in the UK and haven’t yet visited Retromobile, this is a good a chance as any!
see: http://en.retromobile.com/