Cd anyone enlighten me as to why this line is quoted as an 'end' to the Mrs
Porter lines?

The line concludes Verlain's Parcifal sonnet which is the soln to the plot
of the TWL surely?  If only the sonnet were true the TWL could end!

What if the texts quoted in the TWL are taken as running in the background
to the narrative of TWL as the Oddyssey runs in the background of Ulysses?
The lines up to O ces voix then offer a failed harrying of hell as opposed
to the successful harrying recounted in the sonnet.  The line is a flash of
light as the background text momentarily breaks thro'.

Sweeney and Mrs Porter invoke in turn TSE's earlier poetry which must also
therefore be assumed to be running in the background and so giving a
multilayered background which eventually goes to ground down in the
subterranean myth of immediate experience.  That is, the unconscious only
'works' if it remains buried.  Jung is quite categorical that fishing for
unconscious and archetypal elements renders them sterile in the open air,
which is what is happening at the beginning of The Fire Sermon.