Clone operation finished, I couldn't find any obvious way, to force it to boot from the 256Gb SSD, so I tried pulling the HHD. That worked, and continued to work, even once the HDD was refitted. Once happy the SSD was fine, I formated the HDD, to avoid any future confusion over what it was supposed to boot from.
The laptop is now blindingly fast, much faster than it was before, and it wasn't that slow before - except, it crawled if I tried to load anything which hadn't been loaded for a while, and already cached to the Optane drive.
The laptop is now blindingly fast, much faster than it was before, and it wasn't that slow before - except, it crawled if I tried to load anything which hadn't been loaded for a while, and already cached to the Optane drive.