[Solved]
Reset all my settings to default and started over.
Grabbed my PS Move controllers as they’re the closest thing I have to Vive controllers.
Set Steam VR to use Vive controller mapping in Google Earth VR (it still displays Touch controllers, but they function as Vive controllers)
Everything works 🙂
I’m still keen to get things working with Xbox controllers since a mate of mine doesn’t have PS Move controllers, but that’s a different problem.