http://www.saveparliament.org.uk/ - specifically, save it from the Legislative and Regulatory Reform Bill - "Do you like living in a democracy?Well, enjoy it while you can, because it might not last much longer if the UK government get their way."
http://www.votersrevolt.org.uk/ - a much wider campaign - "born out of deep anger and frustration at a political establishment which over the decades has increasingly treated the British public with contempt .... It explains how our democracy is being eroded - and spells out how together we ordinary people can halt the slide INTO phpbb_bureaucratic tyranny."