Sorry but your talking to the wrong chap to explain it as I am only repeating what I have been assured and read from Microsoft.
If you can find the 'Cortana and privacy' page on Microsoft website a lot of it is there. If you ask Cortana if you can switch her off she comes back with an explanation that includes the statement that because she is "fully integrated in Windows 10 she can't be fully shut off'.
If that is not correct then blame Microsoft.
Anyway in case any one else is still reading this my problem was solved last night with yet another update that locked up my tablet while I assume it configured. Suffice to say every thing is back to normal the morning . It switches on fine and power drain does not look excessive.
Thanks for all the interest but think I leave this site now .
A little too confrontational for me.