Hi ,
Fixed the problem!!
So after a week or so of tinkering (Updating drivers, reinstalling the engine etc) I found what was wrong. It was annoyingly simple in the end.
Somehow I disabled the Editor viewport ‘Realtime’ Function (CTRL+R) located at the top left of the viewport. This meant that nothing in the editor viewport was being simulated on-the-fly (Cables included) until I entered ‘Play’ mode. Re-enabling ‘Realtime’ brought all my cables back. Staring me in the face the entire time.
Leaving this comment in case anyone else makes the same stupid mistake 