The Jumper seems to be some selct between horizontal sync and composite sync. In VGA and RGB monitors it doesn't seem to do anything, on the scematics it leads to the modulator so I guess it is do do with modulator. I think that the UK Falcons maybe missing two resistors, 104 and 105. On the schematics these seem to supply colour information. I'd have to see the differences between German Falcon and UK Falcon, I only have latter.
