Many thanks, Graham and Mark, for your help with this. Though it seems 
to get more confusing the more I look!

Mark Jenkinson wrote:
...
> The avg152T1 image is our standard space image and has well
> defined real-world coordinates.  It is these real-world coordinates
> that define it as being right-handed.

Okay, that makes sense. Although I am rather confused that this is 
defined as radiological... Graham's page gives radiological as the 
left-handed LAS system, no?

> any image that maps to the standard coordinate
> system with a negative determinant is considered  "radiological"
> by our definition, with "neurological" ones having a positive determinant.

So you assume that the voxel coordinate system is always left-handed 
then? Such that the negative determinant gives right-handed real-world 
coords. Or am I still confused...

> Personally, I would have chosen different conventions, but we have
> to be consistent with the standard that was originally prepared and
> that was the avg152T1 images (or the avg305 images) which were
> prepared and shipped with the above conventions.

I completely understand that. There's still one thing I'm puzzled 
about: do the medical conventions demand that views are placed 
relative to each other as they are in FSLview, or is this a free 
choice? Because it seems to me from viewing your very helpfully marked 
image that the layout is not consistent with either standard for 
orthographic projection. Moving the sagittal view to the left of the 
coronal would give a valid third-angle projection without actually 
changing the convention within any of the views. Is this reasonable? 
The other alternative (for valid 3rd angle proj) would be to have the 
sagittal view remain on the right, but be nose-left. Incidentally, 
this seems to be the case for viewing the marked image in SPM5, but 
I'm not sure if it's doing anything non-standard to achieve this?

Best,
Ged.