Thanks for all that info everyone but, as ever, I still have a couple of questions!

Am I correct in thinking that if I'm using an RGB or Composite style input, PAL/NTSC etc won't matter to me? So I just need to daisy chain my SCART devices together then stick an RGB-YUV convertor on the end and I'm off to go?
Anything else I should be wary of?

Thanks a lot for that schematic!

Cheers.