Koz, have you tried using Cinema Tools?
that can simply alter the clips play-back speed.
it works betwen 24 and 24 fps, i know
remember i am from PAL land, so dont know if it works from 24 to 23.976
open CT,
it will ask you to open a database, but just cancel that stage.
open the clip (apple O)
and then click CONFORM (lower right in CT v3)
pretty sure this work.
and no nasty re-compression or frame-juggling.
should be an ever-so-slight slow-down & pitch-down of the sound.
hope that works,
nick