So...out of interest if I move the MLP forward 1-2 ft, shunt the sides forward to the edge of the chimney breast and space the rears out at the back more (toeing them out more too) that would help improve things sonically somewhat and increase the effect of the 4 atmos speakers?
Should do. If the pictures are deceptive, then it's difficult really to know.
But, in simple terms, it's about (roughly) spacing everything out angularly between speakers.
The actual guidelines are here...
Dolby Atmos Guidelines