Well, I don't think it's the boards.
Both have different firmwares installed, both have the pre-heat temps at 200/65 and the screen shows exactly the same options and settings 180/50 for both.

Somewhere down the line the screen is just not communicating with the board properly.
I know it's communicating as you can sort of get the stepper motors to move. Albeit the wrong way.
So the baud rate is correct - hads to change from 250000 to the standard 112500 (or wahtever) as arduino ide simply doesn't ever give you and option for 250000. (on of the many reasons I hate it)

I've checked the config and firmware on the screen and as far as I can see it's what it should be.
Board programmed first time without any hassle, so I know the settings went through okay there.

At this stage all I can do is try and find the missing screen. I mean it's already installed on a mount it has to be in my workshop somewhere !