Breaking and entering is a criminal offence though, which is why it's very important on how you do it, even being a civil offence however you have to be careful, can still mean you end up in court.
who said anything about breaking and entering?
and re the link you posted (http://www.freebeagles.org/articles/Legal_Booklet_4/lb4-21.html)
and its very simple, if you meet a security guard, or someone like that and they asked you to leave, you do. and you be polite to them - as you shouldn't be there. but you don't go smashing into places, breaking stuff, mouthing off, or nicking stuff - nice to see this thread has missed the point of urbexing!