Update:
I have added the line vfs.root.mountfrom="ufs:ad0s1a" to /boot/loader.conf and it now works fine.
Can anyone give me some clue as to what is actually going on here?
This box is a new model that I suspect many people will buy. There MUST be a better way to install than this?
Thanks,
Chris
PS.
Instructions to install that work for me:
Run LiveCD with a blank USB stick in the front.
Select install to Hard Drive. When asked, select the hard drive ignoring the USB device.
When it asks about the boot blocks, disable packet mode. Disable everything on the USB stick as it is not needed.
When the device reboots at the end of the installation, power off and remove the USB stick. Power back on.
It now boots but stops and asks for the root filesystem. When prompted enter: "ufs:ad0s1a"
Follow normal install process.
Once it is running edit (either through the UI or through the shell) /boot/loader.conf and add the line:
vfs.root.mountfrom="ufs:ad0s1a"
All Done!
YMMV