To Neil,
We deal with this all the time and I understand a minute of audio is a minute of audio. What happens is this. We receive source footage from 25fps source. To convert properly, you interpret the 25fps footage as 24 or pulldown 23.976. The video now plays 4% or 4.1% slower. The only way to fix that is to pulldown the audio. I have been using Waves Soundshifter for years as it seems to keep the pitch correct and add the smallest of artifacts. The only other way is to mess with the video which is quite intensive. You get a lot of frame stutter if keeping the timing the same, so you need to deal with Frame Blending which can be quite a tedious process.
I hope this helps to explain a bit.
Grant