Hi.

My MMI has has White Screen. I've checked fuses,  bought a new Screen and done fibre optic bypass tests.The Radio still plays and there's some functionality on the mini screen on the speedo cluster.

I have also changed the main wire that runs from the mmi to the box located behind the glove box.

To give you an idea I had to remove the glove box to get to this component, situated up and right of the glove box.

Any help will be greatly appreciated 

You've done a great amount of diagnostic work. Might be worth changing the mmi unit next.