The Synology DS418 and 4x 2TB drives arrived very promptly from Servers Direct (I can’t recommend them high enough for price and speedy delivery).
Slotting the disks into the DS418 chassis was extremely simple and required no screwdrivers.
I plugged the unit into the internet, powered it up and watched it run through its validation and OS and app updating process.
Then I logged in as admin, created the user profiles that my old NAS had, and then plugged in the EDD and copied all of the data in to the profiles.
Then I rebooted the DS418, logged in as my main user, checked that everything was exactly as it had been on the old NAS and that was it.
Nothing else to report.