Just checked and you're right... bad example, I should have checked before I posted. There are, however, plenty of larger companies that did just use a link in the footer (Amazon was one). The day before (IIRC) the deadline for having the law applied, the ICO decided that implied consent could be used, thus making a link in the footer perfectly okay.
The ICO's interpretation of the privacy law requires the user to understand that continued usage of a website will result in tracking (i.e. alert them until they agree), so the BBC's version complies better with the recommendations.
That's what they mean by implied consent – the user can use the website so long as they understand the situation, they don't have to physically agree. A lot of websites then decided to take their own meaning from the term "implied consent" without reading the document.