This red headed lady is a stranger to Lynne, who is merely being kind by commenting on her baby. People who are friends do not say 'Lovely baby' to each other; they would call the baby by its name especially if the baby is as old as that one which must be over 6 months. So if this lady is a stranger, do strangers really say that they aren't sure who the father is? At this point Lynne should have made her excuses and left. No, Lynne is kind and she suggests a DNA test. She probably expected to be told, 'oh OK thanks' and the conversation would be over, but what we get gives an insight to a strange relationship this lady has with her ex-lovers.
The joke of Dan, Nick or Alan is a play on the letters DNA, we know that. Does the lady know that? We don't know. What we do know is that all three ex-lovers are following this lady round town together. Are they all friends? Did she enter some sort of sordid night of sex with all of them at the same time? I think they want some more. Have they been doing this for the last 18 months? Also quite a coincidence that they are standing in that order. Then again we have no way of knowing which one is Dan, Nick and Alan. Two are grey which suggests they are seasoned players in this town's seedy underbelly. I wonder how many other children they've unknowingly sired.