Well, it appears that the VCR is actually just outputting a composite
signal. The problem (at least with the TV-output from the computer) was
that it was only outputting an S-Video signal. With the DVD player, I
assume it must be as others here have suggested, that it was outputting
NTSC.

Anyway, I guess I'll have to work out how to convert S-Video to composite.
I found a simple schematic online (just connect a 470pF capacitor between
Y and C, and tap the composite signal out of the Y pin). This doesn't seem
to work for me, as I just get a black screen with some scrolling
distortion. Has this worked for someone else here?

Thanks,
David