I can't understand what would be meant by poxy head. Foxy head surely makes more sense in the context of the song. You still hear the term used in Ireland btw .
I hear the song as a battle between two women, one with a husband in the army ,the other married to a slacker (perhaps it was originally sang as a comic duet?). The army wife wonders whether her husband is dead , Mrs Slacker wonders whether he knows that his wife has had a kid from another man while he's away.