Regarding my scratched Astro Boy disc:
As I had a bit of time, I did my standard test for these kind of things.
Basically, I stuc the disc in my DVD dec and played through the whole thing in fast forward at three times playback speed. This is usually adequate for me to spot any playback issues. And I didn't see any, so I might be good.
I might give that disc a sort-of-kind-of-semi watch tomorrow while I'm working as well. Which will ruin those episodes for me. But at least I'll know if the disc is buggered or not.