OK further resolution update.
The tech guy at the supplier, tested the MB and the CPU and found both faulty.......his testing was not intended to discern what & in what way the failure occurred but the items will be sent back to the distro/ manufacturer. When I asked, he simply said sometimes equipment just fails and 'they' declare it so.
So, he took a new MB & CPU from stock and "took the liberty" of testing them together and 'they' started and allowed access to the BIOS screen......which is the limit of the steps he took. He removed the CPU, cleaned it up and refitted the LGA1700 socket guard etc, boxed up and to be dispatched tomorrow on their 24 hr service.
PS I asked, do they routinely flash the BIOS and he said no.
I mentioned my discussion with Gigabyte eSupport and he said typically BIOS flashing if there is there for CPU compatibility reasons.
Note ~ the eSupport reassured me that even though they say to flash the BIOS to make it work with nVidia RTX3060...............it (now, I told them at the outset that my GPU was a Gigabyte one) seems that their own brand of the RTX3060 (integration) was AOK even with BIOS version F1....and the newer F4 BIOS was aimed at the compatibility of the other brands of RTX3060.
So all being well "all will be well".
PPS cynic and 'belt & braces' person that I am......as mentioned I took photos of the items returned and will be checking the serial numbers against the numbers on the boxes. However, I found an Intel phone app to get the CPU serial number from the 2D barcode on the CPU. It even worked by printing the photo of the returned CPU and the number of course tallies with the box
Edit and FWIW this is the Intel page and app....I went it Google Store for it
Describes Intel® Reverse Logistics Toolkit and how to use it to find your Intel® processor serial number.
www.intel.co.uk
Lastly, all being well the re-build will go 100% AOK and this time I will, as mentioned (somewhere above) start with a vanilla install of the Win 10 OS....just need to have all the elements to hand to install "my stuff"....sods law says I miss something.
The one pain as I see it, re-doing my Outlook 2007 emails folders because I cannot find a way to somehow copy the folder structure and import that into the new installation
Oh, another one is installing my HP Laser....though on WiFi it needs the USB cable link first.....now where did I put that particular cable