There are a number of websites that can help you to complain effectively. Links to these websites are available under Other Websites.
Directgov Making a Complaint
A guide to complaining to all levels of government from the central government portal. They also have advice on reducing spam and junk mail.
Independent website that allows you to submit, escalate and resolve complaints online, and talk to others about your experiences via message boards.
Watchdog Guide to Complaining
Advice on the BBC website from Watchdog on the art of complaining.