In the UK the age of consent is linked to the age of marriage, we wouldn't give two 13 year olds permission to marry so we should not give them permission to have sex.
Underage sex happens, but just because it does doesn't mean it should be normalised and/or made legal.
Keep it at 16 or raise it to 18 and introduce a 'Romeo and Juliet' clause to give some protection but not an absolute one. Also start prosecuting those who are exploiting children.
I watched a 2 part documentary about the Soham murders last week, Ian Huntly had several complaints against him for having sex with children one of whom gave birth to his child.
Apparently she refused to give evidence, but that IMHO should not have stopped him being prosecuted.
As for 'barely legal' porn, in the 1980s the Sun had a circulation of about 3 million, it also frequently featured a 16 year old Samantha Fox, so 3 million people had no problem buying a newspaper in which a child posed mostly naked.
That says a lot about our society, and that is what we need to change, children should not be having sex, adults who do have sex with children should be punished, it should be unacceptable and historical cases should be prosecuted now.
Bill Wyman should be prosecuted, I'm not sure why he hasn't been.