Tried to reinstall bootcamp windows 10 using windows media creation tool and mac mini wont boot-up

It's been a year since I set this all up and its been running fine, but I needed to reinstall Windows 10.

I downloaded the Windows 10 media creation tool and ran the setup in my windows partition.

It rebooted and tried to boot into windows but failed with a black screen.

I am now stuck with a bricked mac mini, I've tried all the start-up key combinations and none of them now progress beyond a blank screen, there is no audible startup beep.

I suspect windows has corrupted EFI of something similar.

Can anyone advise the best course of action? Is there anything I can do myself or will it need to go back to Apple?

Any advice greatly appreciated.