IIUC, Trespass is a funny old law. I believe that if someone enters a property but has caused no damage, the worst that can happen happen to them is to be asked to leave.
Whoopy-Doos!
Under railway bylaws the CPS does have the power to fine trespassers, provided that a clear notice was displayed telling them not to (like they should need to be told

), but if they enter property at a non-approved place, eg a hole in a fence, then that rule won't work
What we need is a law such as "entering railway property without authority or the recognised training". Bang, woosh £1000 pound fine.
Or similarly "Causing economic/financial damage to a business". Since any railway looses money when the trains are made to stop, how about making the twonk who is responsible pay for it?
Yes I know, there's not a snowball's chance in hell - but that's how I'd roll on Planet Johnny!
Keep safe, John