What you're saying is that it's ok to land without PPR and then refuse the landing fee because you don't like how much it is?!!
Quite right. However, as Piperboy84 said, you can then refuse permission for them to take off again, and place obstructions around the aircraft, as long as you don't damage it or endanger it in any way. If they really want to leave you could offer a take-off fee that they are free to accept or reject - but the point that got us into this is that once money comes into it the landowner has to consider what he could be making himself liable for and how he might mitigate any negligence risks. A box for voluntary donations towards upkeep (mowing) is one thing, but a set of fixed charges is another.