My thanks again for all the help. All is as it should be now except that I am waiting for a pair of X5675 CPUs. Unfortunately the X5690 CPUs didn’t work.
Leaving out my own ineptitude and mistakes I believe this thread should be closed with a successful outcome so thanks again.
For future reference there have been two issues which have been more particular to me rather than of general interest.
The first is the installation ab initio on newly built hardware RAID which had previously not had any partitions installed and where there was also a PCi NVMe drive. I was trying and failed to install only /boot and /boot/efi on the RAID I can only conjecture but it appeared that the installation probing went past the array and tried to install on just one of the drives. This is probably a bug in the hardware raid firmware which I have not been able to upgrade since 2017. It was easy to work around this once I knew what was happening.
The second issue for me was when moving the /boot and /boot/efi partitions from the USB to the hard drive. I made an omission error in copying these partitions with contents. To sort out my mistake I used a Live version of Leap 15.3 and used Dolphin in Super User mode to copy these partitions across. This all worked as hoped but I was not conscious of the fact that the partitions, although separate, were both visible in the one gui window and not seen as separate partitions. Just my ignorance, only my problem!