Update to my earlier post:
It's all good! Apart from..
I was using Google Chrome and nothing else and it suddenly seized up.
I don't know why I have to press ctrl-alt-F8 to get the desktop instead of ctrl-alt-F7. When installing, I got a message something like "can't use screen 0, use 1?" to which I replied "yes", so perhaps everything is shifted along one. Though why I got the message in the first place I don't know.Seizing up
It has seized up again, I was pasting a web address into a LibreOffice document table. I had Chrome and LibreOffice Writer open.
I have tried it again and again: boot up, open Chrome and Writer, cut web address from Chrome address bar, post it into Writer table. It happens every time, everything locks up except the mouse cursor and ctrl-alt-F*. I can do ctrl-alt-backspace to log in again.