It depends what you have got to lose if like myself you have shotgun and firearms certificates you could have them taken off you if you get into any bother the old bill dont need a lot of reason to revoke your certificates hence why i would never bother poaching ferreting is easy enough to get without poaching have you asked the farmer ??
But other than that it proberly isnt worth the paper work to the farmer or the police when i started ferreting when i was 15 many moons ago LOL we used to just go ferreting where we wanted got caught loads of times and just told to get off or f**k off the l