How do you mobilize people?

Having lived in the UK for around 11 years, it strikes me to see a nation that is not used to protesting against their Government. People complain about the political situation and disagree with it, yet they don't do anything to try to influence politicians or to stand up for themselves. To a person who comes from a more active Scandinavian culture where people are not afraid to voice their opinions, this culture of passiveness seems odd.

An example of this passiveness is the fact that most British people are against the war in Afganistan, yet they don't do anything in order for the Government to know how they feel about it all. (http://solomonsmindfield.blogspot.com/2010/07/only-17-of-british-want-troops-in.html)

Another example is the threatened cuts in the public sector and in public services, which people oppose, yet don't voice their opinions to those in charge of making such decisions.

Is it just culture of passiveness, of not caring, or is it simply that people don't know how to go on about voicing their opinions or opposing policy makers?