Thankyou I was aware of that and had been toying with that idea when I stumbled over this one.
On reflection I would like to clarify:
Select Power and Sleep
Under Related Settings select additional power settings
Select Choose what the power buttons do
Select Change settings that are currently unavailable
Under Shutdown settings click off Turn on fast start-up
This ought to restore Left-click start menu, Cortana, notifications, calendar etc
Once this has worked for you re-enter settings as above and click on Turn on fast start-up
This will return your pc back to the way it was and saves all the aggravation of setting up new accounts or getting involved with re-installing Windows in any way.