I think I may have figured out a way to finally centre the camera properly. There's a setting I wasn't aware of that seemed to work. As you might have guessed by some of  the inconsistency,  I've had to eyeball the centre and I usually think I have it properly centred until someone points out that it isn't!

VR 

VR high bitrate 

VR h265 

VR h265 high bitrate 

PSVR