Maurice,
He is not asking where to camp; but rather, where to camp so as to minimize contact with other campers. This can be an interesting discussion.
In the US many of the places that I use to camp in as a kid have closed to the public. The camping population/enthusiats has increased widely with the improvements in technology and confort. This has put pressure on landowners who have become increasingly concerned with property damage, and personal liability.
My suggestion is to contact some of the major property owners in the area you are interested in and work out an arrangement that allows you to use the property. Sometimes this can be as easy as a phone call, but its becoming increasingly important for all of us to act responsibly when in the woods.
Hacking live trees down while in a private forest preserve, building dangerous fire hazzards, and leaving garbage behind, are all to common example of irresponsible behavior.
Do low impact camping or we will all be limited to camping at the local KOA.