I could say touche', Nigel - but I won't. There's a very fine line between the ridiculous and the sublime. "St. Patrick's Breastplate" does indeed have lots of prepositions - but it works.
Look at my "Preposition Song" again and see the difference:

Above, below, and around me,
Before, behind, and all through me,
Your Spirit moves deep within me,
Fire my life with your love...

"Patrick" is profound. "Preposition," to me, is ridiculous. I think part of the beauty is in "Patrick's" parallel structure, a device that has been used very artfully in hymns all the way back to the Psalms. "Preposition" is just that - an unordered list of prepositions.
-Joe-