Some major (for me) surgery on the TR6... Clutch replacement time which means either taking out the engine or taking out the transmission. The latter is the recommended approach, which also entails removing most of the interior. I guess Triumph had some Germans working for them when they designed this.
This of course means dealing with old, nasty carpet underlay and fiber board covers, plus various rusted, broken or seized bolts. About at the stage to separate the trans from the engine now. Once that's out of the way I can get to and replace the clutch, then just have to put everything back together again so likely another couple of weekends (or more) work ahead, but hoping it will drive much better once done...