Because at present Great Britain isn't great!
We can't "make" civil liberties for this country without first having an agreed (not assumed) framework of what citizenship is and is not; of what are responsibilities and rights. Consult any ten people and a wide range of opinions will emerge. What have other respected nations done successfully? Does the american citizenship model create good citizens? (Leaving out the inalienable right to bear arms.) Freedom doesn't exist in a vacuum, giving everyone the right to do anything anywhere won't work. Let us look at other nations and see what's working and why it works; perhaps we can learn new ways of being Great Britain.