A version (with nothing new here) is in The Oxford Book of Light Verse (W. H. Auden, Ed.) The version in The New Oxford Book of Light Verse (Kingsley Amis, ed.) is credited to that one, but is "supplemented by oral collection", including the following digression on her pleasures while the second affair lasts:

See them at the gay theAter
    Sitting in the costly stalls;
With one hand she holds the programme,
    With the other strokes his hand.

See him have her dance in Paris
    In her frilly underclothes;
All those Frenchies there applauding
    When she strikes a striking pose.