So after all the grief with Xen and Suse, I started again. Trashed the server, installed firmware, hardware RAID etc and then a fresh install of SLES12 sp3, all standard settings except I did a custom disk setup as follows: vfat boot and swap of 2.gb then the balance 2.7 tb to / .... all kool! Installation goes perfect and reboot. Server comes up and can ping the universe, see the disks, etc etc. Install Xen Virtulization Tools, again the defaults. Changed the BootLoader to "SLES12sp3 with Xen" and shutdown. Power up and the server gets to the BootLoader screen and the "Sles with Xen" option starts, the screen clears and the server does nothing further. mmmh, power off and then on. The server gets to the BootLoader screen and I select the "Sles" option the server boots and all is good.

I have looked in the logs but have found nothing that refers to the Booting of the hypervisor ...

As usual: suggestions, comments, tips, cash or laughter will be appreciated