Nikon 70-200 VR Noisy

When I half click the shutter button to focus, the lens makes a quiet grinding sound for 1.5 seconds. Whether I've taken the photo or not. There's a small chip on the lens hood where it's clearly taken a knock so I don't know I this could've caused any damage. Any advice or insight would be hugely appreciated.

Sounds like you have damaged it. For the price you paid, I certainly would have it fixed.

I know that stabilisation systems do make a quiet hissing noise when it's activated. Most IS systems remain disengaged, only activating when you half press the shutter button.

It's hard to say as I'd have to be hear it to be 100%, but from what you describe, that's pretty normal for VR systems.

Sounds normal to me. Mine does, too. Thats the gyroscopes working away to steady the image.
Mine makes the same noise for the same amount of time.
Excellent lens to boot.