[cojms1]

It's worth a try.

I'd also try playing with:
adjust display refresh rate to match video
sync playback to display
Adjust PLL
Resample method (gpu/other)
Audio passthrough

And report if changing any of those settings avoids the problem.

I think I've identified what is happening. I've tested this on another TV and didn't seen issue there. So it looks like it was particular to the setup I mentioned previously - Pi --> Marantz --> Sony TV.

It appears that the TV causes lag when going through "Bravia Sync" at 50Hz. Since I switched Kodi to adjust the display refresh rate to match video (stopped my jerky video I was seeing) the audio sync seemed to be more pronounced (hence me seeing it now - no idea why it seemed to be more pronounced on PVR, I actually don't think that was the case now). I've added the following into my advancedsettings.xml and now everything seems to be playing nicely - from all sources.

Code:

<advancedsettings>
  <video>
    <latency>
      <default>0</default>
      <refresh>
        <rate>50</rate>
        <delay>200</delay>
      </refresh>
    </latency>
  </video>
</advancedsettings>

Sorry to have bothered you with something that seems to have been very localised to my TV.