........immobile with no drive thru' clutch - feels like usual clutch plate wear/failure but only 10k since new plates fitted and oil leaks on both slave and clutch side - bit puzzled by this one.

Knackered clutch pack - replaced with set from spare engine.

Last set were installed with notched friction plate tab in random positions, as I thought was recommended, but having checked manual, seems they should be all aligned - could this random friction plate installation have caused premature wear of friction plates?

well at least you know what happened….

Think they should all be aligned except for the final plate before the pressure plate. Move this one notch round

Yep, installed like that but forgot to mention the last plate - not clear why the last one needs to be rotated by one tab though.