From what I've read, the modified Erich Demant propshaft with HD universal joints and grease nipples is the way to go for trouble free long distance riding, and this seems to cost in the region of $250 or thereabouts.
Question - What actually does he do to the propshaft? I believe the UJs were staked but he machines grooves for circlips, right?
Question - What HD UJs does he use instead of the OE ones?
Question - Is this modification something any UJ repair ship in the UK can carry out or are we talking about specialised engineering work?