can anyone else shed some light?

Ok, since nobody else answers I'll give it a try. I recently changed the transmission mount, the rear flex disc and the support bearing of the driveshaft on my W124. Based on this experience I'll say that you do not need to remove the transmission support bar but you need to collapse the driveshaft by loosening the big sleeve nut (and unboltung the driveshaft boot). In my case the flex disc was almost baked to the driveshaft and was hard to separate. Sensible use of an air chisel came very handy at this place.
Good luck, Bruno

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1992 300TE 160 kmiles

Have just seen your e-mails as I am about to replace the vibration damper on my C180. If you have replaced your's yet I guess you found that removing the cross member gave better access. I believe the sliding joint allows the front propshaft to be moved back. Is this correct? Did you find that the vibration damper could be easily removed once the bolts were removed. My flexible coupling looks OK so I plan just to remove the damper. I believe the centre of the propshaft only needs to be disturbed if the rear flex coupling is to be replaced. I would be grateful for any advice.