The engine and gearbox do wobble considerably when sitting at idle, as does the gear lever. Not having any experience with these cars previously I assumed it was just a feature.
Pretty sure I ruled out the prop & UJs by running it in neutral.
Failed mount(s), speedo cable or clutch linkage would be happily easy remedies so are my favourite theories.
The car drives fine, very nicely even, it just sounds like a death metal Christmas sled.