The error it throws seems to be fairly well known.
According to the web the most common solution is replugging the USB install stick in a different port which is a tad difficult with it being a LAN install.
Another possible cause would be a corrupted iso so I redownloaded it again with the MS media creator tool but that made no difference. I tried it with an iso of windows 7 as well I have laying around but that gave me the same error which made me believe I wasn’t mounting them properly. Hence my earlier question.
Unfortunately I don’t have an USB stick big enough at hand to strike off that possibility. It’s one of the reasons I wanted to do this over LAN. Same with a cd, I don’t even have a drive let alone a burner.