Quick update, it's going to survive.
Gave it an almighty root prune in late Feb. Also removed a number of unwanted branches but left extra on to try not set back the tree too badly.
It's now finally bouncing back after dropping nearly all of its foliage. It was kept in a water tray in a shaded area up until today. I have now removed the water tray but will continue to keep it in the shaded area to assure it doesn't dry out too much before it can really get settled.
Photos attached of its current poor state awaiting some new foliage.
Cheers,
Pearcy.

Sent from my SM-G950F using Tapatalk