Hi Trevor,
your choice to sail from Newcastle to Amsterdam sounds quite reasonable. I did this trib 5 years ago, beside of some handful of very loud drunken dutchmen it was enjoiable. There was also a connection to Hamburg which I took for my way up to Scottland. I am not sure if that line exists any more.
If you're coming from Amsterdam and you wants to reach Bavaria you have first to ask yourself how much time you want to spend. If you want to go as fast as possible the route is very simple. You'll first take the motorway E35 from Amsterdam to Arnheim, further over Cologne to Frankfurt then continue on the E42 and E45 via Würzburg and Nürnberg, the n on the E56 to Regensburg. From there it is best to leave the motorway and to drive over country roads to Landshut, further to Vilsbiburg, Neumarkt St. Veith and then you're almost in Roßbach. With the invitation there comes a detailed map of the nearer surrounding of Roßbach.
That is the "Express" route. If you wish to get more detailes please feel free to contact me directly over my email adress.
Regards from Augsburg
Armin

Heast, meine Turbo-XJ ist ein piekfeines Renngeraet, da gehoert halt eine Verkleidung drauf. Aber die Scheibe ist doch eh abgeschnitten:
http://koblenz-net.de/~horn/turbotreffen_ochtrup_2005/cimg0027.jpg
Links Original, rechts mit hornschen Modifikationen...
Und: Selbst mit einer BMW taet ich dich immer noch herbrennen. So. ))
Gruss,
Georg