Thanks for the prompt responses. Problem has been resolved.
When playing with settings for Notes, I discovered under Setttings-Notes-Accounts, Gmail was ticked and I did not have Settings-Notes- “On my iPad Account” switched on. As a result all Notes were being saved, to the All Mail folder, on my Gmail account and all deleted Notes were in the Bin of my Gmail account.
I switched on “On my Ipad Account”, returned to Notes, created a note under “On my iPad”, then deleted the newly created note. I am now able see a Recently Deleted folder with the note I just deleted.
Not sure “On my iPad Account” is switched on by default, but I have no recollection of when, why or if I switched it off.
Anyhoo all good now.
Thanks again.