Hi Darren,
Do people get robbed? Sure they do, and not just in France - but all over, and that includes the UK.
The stories one hears seem to have the recurring theme that people "take a chance" on sleeping in motorway aires in certain regions of France and Spain, rather than stay in a real camp-site over-night.
Stay at camp-sites and you shouldn't have a problem.
And France, Belgium and Holland are great places for a first trip - especially Belgium and Holland if you aren't gifted with languages (where English has been universally taught as a standard subject for the last 30 or more years)
So - try it - we love Europe, Robert
P.S. The subject of gassing, as opposed to just being robbed, is quite emotive - and as a scientist and engineer I'm just not going there - the important point is not to expose yourself to undue risk - and that applies everywhere.