Yes you're quite right jomifl. And more to the point it doesn't really matter.
TV drama is just that - drama. It does nor have to be representative of real life. It does not have to contain the correct proportion of black people, gay people, straight people, drunks, criminals, young people, old people, vicars or tarts. It is quite true that the proportion of ethnic minorities in most urban areas is far greater than in some rural areas, but somebody from the shires might well suggest that programmes like Eastenders are "too black" because many of them may well not see a black face from one weeks end to the next.
My original post was flippant (and in fact I was surprised that my description fell foul of AB's censors, because the blanked out word only related to the red stuff that flows through our veins). TV drama does not have to reflect or represent real life.