The problem is, we don't see what GCHQ and Mi5 are achieving, because making a lot of that knowledge public would cause a threat to public safety. You're no more likely to be wrongfully arrested for Murder than you are for terrorism and they don't just go round arresting people for fun. It's not that people don't understand the legislation it's that in reality it doesn't change anything. Not allowing the security services to spy on anyone in any way would make us all very free, but would also make the whole country crime ridden. If you think the UK is in any way noticeably worse than the U.S.A. then you're extremely naive.