I tried using the @BIOS utility to install the BIOS File I had already downloaded (F18) and got the same error as before. I told it to carry on and update anyway but system wouldn't boot so I restored it to the original BIOS and tried the "update from Gigabyte Server" option. For some reason the most recent version it could find was F9, when I tried to upgrade to that I got a warning: "This is not a regular file name" I ignored it and upgraded anyway and again it wouldn't boot.
Thanks again for getting back to me, any other suggestions would be appreciated. I'm totally stumped...
I've now managed to update to F9. I got the same boot error as before
"'Remove disks or other media. Press any key to restart"
So I entered the BIOS and looked at the boot options. For some reason my internal SSD was showing up as a flash drive and was not a boot option, I set this to boot first and the system seems fine. Curiously I still can't upgrade to F18 as the Gigabyte servers only have F9 and the BIOS files I used before now just give the error "BIOS Partnumber is not correct" with no option to override.