The whole thing is a bit weird. I accept that years ago, it must have been very very common amongst working-class families for the parents to have sex while there were children in the room. You'd have these enormous families of six, eight or ten children, and only two bedrooms - so it was inevitable (unless you abstained altogether).
I find it strange that a modern-day couple with only one child have to do this, though. Perhaps they just have the one bedroom, but when you have an eight-year old child, you might expect them to give him a sofa bed in the living room.
But I tell you what's really odd - the whole bloody idea of this series. It entails a couple agreeing to be interviewed individually by a journalist about their sex life, to be published in a national newspaper. What normal person does that? What normal newspaper publishes it?