did a bit of reading, CROW section 2 which i think is applicable only gives rights to walkers, not cyclists or horses.
But tresspass which is the most they could go for is a civil matter and not a criminal matter, they can use reasonable force to ask you to leave, they could ask for compensation for damage caused. But as the trails are already there and well bedded in what damage will be caused.
I really really hate this English idea of “my property”, if this was a garden or a field then maybe i could understand not wanting people to have access, but it is not it is ancient beech woodland, it has been used for decades, i have ridden there for over 15years in total, and it was in use before i started riding. If they want to raise a fence around the Tump fine, it is a scheduled ancient monument afterall.
How do they intend to keep bikes out? i may get annoyed by the County going through with a group of 15-20 riders, but it does happen. i see plenty of smaller groups, 5ish. plus solo riders. A sign saying keep out isn’t going to work.
They would be better off putting up honesty boxes and asking for donations.