There most certainly is! Where do we begin?
First, campsites themselves are a lot cheaper than in the U.K., especially the Municipale ones.
Second, every town, and most villages, have an Aire de Services Camping-Cars, offering water, black and grey waste disposal, and occasionally electricity. Inland, these are often free, and always cheap (rarely over 10€ a night).
Then there's France Passion, a network of farms, vineyards etc where you can stay free, with no obligation beyond being sociable. You join by buying the current year's book, which Vicarious Books sell - usually less than £30.
And finally, there's the very different legal situation. As long as you don't put anything outside the vehicle, you're legally "Parking," not camping, even if you're cooking and sleeping. Although many coastal places now try to prevent that along the front, they can only get exemptions to do so if they provide an Aire.
All of which means, far more money for the motorhomer to spend on food and drink!
Enjoy your trip.