Thank you to Brian and Diane for saving me from looking through the maze of
options to find the magic tick box that would sort out my problem.
Looking at it again with the knowledge that something in my profile was
wrong, I discovered that the "check names" button on the exchange server
settings page was greyed out. I made a note of the server address and changed
it to the one in my full email address. This activated the button, so I
pressed it. After finding my name, outlook then reset the server name to what
it had been earlier.
Thinking that this might have solved the problem, I re-opened outlook, but
reply to all still included my address in the distribution (and my outlook
today page had disappeared!!!)
I closed outlook and went back to the exchange server settings page, changed
the server name again, but this time didn't check the name so the server name
would not reset. I now have my outloook today back and I can reply to all
without having to remember to delete my own name every time.
Thanks again to Brian and Diane for putting me in the right direction