Strangely, by pure coincidence,............ surely not!
Yesterday CCleaner offered two updates one very soon after the other. This morning Windows prompted a restart due to an update. So I updated CCleaner twice yesterday and before restarting in order to update Windows I ran CCleaner. Ran it as I always have done without any Office products ticked on a Custom Clean. Then restarted, Windows update installed and ran Office Outlook followed by Word and then Excel. Without issue they all opened as they should without any notifications of corruptions of any sort. Coincidence or updates fixing things? I don't know but I will plod on and keep a close eye on things. Any issues I will report back here.
Please accept my humble gratitude to those that have got involved and tried to help me with this rather frustrating glitch.