If you are logged in you can now choose how the mouse position is displayed in the box top left. So rather than just being NN99999999 it can now also be NN999999 (which is certainly how I was taught to state grid references, but is only accurate to the nearest 100m) or even NN9999999999. You can also choose to display it as a completely numeric grid reference (only really useful to map nerds )
You change how it's display in the settings popup, as shown here:
As you can see I've just set the display of the mouse position to numbers only.