The BBC run a centralized duty log for dealing with all complaints about their radio, television, internet and teletext services. All minor complaints should be reported by telephone to this number. More serious complaints should be sent by conventional mail to the Programme Complaints department. I have only done this on one occasion, when a Ceefax page was misleading, factually incorrect and showed many signs of double standards.

To recap - if the complaint is:

A minor irritation
Call the duty log on with your comments on +44(0)8700 100 222
More serious
Call the duty log on +44(0)8700 100 222 leave your name and number and request a response
A serious breach of standards
Write to Fraser Steel,
Head of Programme Complaints,
Broadcasting House
W1A 1AA.
United Kingdom

However friendly and helpful the person on the other end of the line may be do not expect a response to your complaint. If you know of a more effective way of complaining please node it!