RE: BATS - The simple answer is don't go into mines that are known to be bat roosts during the bat roosting season - go at other times of the year - the mine will not look much different 😉 simple simple simple. Besides, the bat huggers take great delight in weilding this stick and the odd prosecution really boosts their feelings of self worth.
For reference, does anyone know the last time anyone was prosecuted for disturbing bats in a Devon or Cornwall mine?
RE: TRESPASS - this is really a civil, not a criminal issue. If you are caught tresspassing on private property, the land owner can ask you to leave. You should then leave. If you don't leave they could use reasonable force - but that won't help access! The rules are different on some MOD property.
RE: BONA FIDE - calling yourself bona fide does not make you bona fide any more than standing in a garage makes you a car. There are several well known 'bona fide' mine explorers in the area who would not hesitate to remove a nice crystal from a mine (particularly if no one was looking) yet they are generally the ones shouting loudest about it.