LIke Spaced, I don't believe in masking reality. (In my opinion the Diana road crash pictures should have been on the front page of every newspaper and on every TV screen. Similarly, we should be shown the full horrors of war in news reports, including dead bodies, beheadings and people dying in agony. Equally, I have no problem with the portrayal of sex acts, both 'natural' and 'unnatural', between consenting adults).
I don't particularly like so-called 'foul language' but I don't have any great problem with documentaries using unedited content containing it.
However, I also believe that AB should be a source of accurate information, so here's the answer to your question:
Since 2003, the duties and powers of the former Broadcasting Complaints' Commission have been absorbed into those of the Office of Communications (OfCom). They receive, and respond to, complaints about individual television programmes, as well as more general issues. Complaints can be registered online, here:
http://www.ofcom.org.uk/complain/progs/
Chris