Again annother "no legal knowledge" response.
Regardless of what machine (or not) is used to enter someone elses land.
If you do enter, the law(s) which apply would surely be that of trespass?
If I understand it correctly that means the landowner can only recover the costs for any damage caused.
It is this which makes the trespass laws regarded as weak by landowners as walkers (for example) will cause no real damage on a grass field or by sticking to the hedgerow, they can only tell them to leave.
Of course using a vehicle or aircraft might be likely to cause a little more damage.
When a glider or balloonist offers a bottle or flight what they are actually doing is compensating for any potential damage, if there is none the landowner might feel they done OK from the deal.
I'm not convinced there is any "right" to levy any charge or to hold prisoners pending payment
The legal right would surely be to charge only for any actual damage and if disputed settle this through a civil court.
Preventing an owners enjoyment of thier property (aircraft) for an extended period plus any additional costs resulting to the owner during that time might well outweigh any "damage" to a grass strip?
If this is a case of a new landowner not wanting a previous grass strip to continue in use then painting the white crosses would seem the most effective way.
PS: did manage to find this
"Note that s76(1) of the Civil Aviation Act 1982 provides that no action shall lie in nuisance or trespass by reason only of the flight of an aircraft over any property at a height above the ground which is reasonable. However, s76(2) confers a statutory right of action in respect of physical damage caused by aircraft, actionable without proof of negligence."