For more information, look at www.legislation.gov.uk and search for the law that you want to read.
Or you can, of course, look at this copy of the NETCU (a police unit which has now been dissolved – see under “Misc / Activism” for more info.) handbook, originally helpfully dropped by an officer policing a Climate Camp and now uploaded on to the web:
NETCU Handbook (pdf)
Also see the “Pocket Guide to Your Rights” produced by an activist with much experience and knowledge of the law: Pocket Guide to Your Rights (pdf)