Hi Everyone,
I wanted to provide an update to my issue and also thank everyone for providing their suggestions and online diagnosis! To those who called out the engine mount, bingo!
One of the engine mounts had the bolt completely missing from it. So it was assumed it wasn't torqued properly and eventually worked its way out. The other mount had the bolt head snap off which meant half the tread was inside one end. The conclusion there was that the second mount failed due to the extra stress of the first mount failing. That caused the engine to move slightly downward and forward, resting on the front cross member which caused the awful vibrations and resonance.
An inspection of the transmission mounts identified one of the two mounts being loosely secured and so was re-torqued.
All of this after another workshop installed new engine and transmission mounts in August 2019 (before I purchased the car) and the car only having travelling 1,000kms. I'll be having a word to this other workshop but I presume it will go nowhere especially as I'm in another state... I'm of the belief they should foot the bill for this and will be asking!
Back to enjoying the car once I pick it up on Monday.
