I tried using the repair button and noticed that it was connecting briefly and then dropping off again. Previously, I've had to go into Advanced Settings and check the box to tell it to use Windows to configure the network. When I looked, the box was checked so I unchecked it and here we are, up and running again, As I said at the start, I'm way out of my depth......
Many thanks to all who offered some help, especially you, Joe, I'll buy you a beer someday if we ever meet up.