I have managed to get it back working as a telephone!
I did the following steps:
- Back-up phone to computer.
- Erase without restore
- Warnings that it wouldn’t restore the iPhone because it needed an update.
- Sure enough when the iPhone came back to life, it would not restore.
Put your device in recovery mode and set it up again
https://support.apple.com/en-gb/HT201263
- On a Mac with macOS Mojave 10.14 or earlier, open iTunes. If iTunes is already open, close it, then open it again.
- iPhone 7 : Press and hold the Side and Volume Down buttons AT THE SAME TIME. Keep holding them until you see the recovery mode screen.
- Told me it was going to recover the iPhone.
- iPhone 7 came back to life and Vodafone appeared!!
- With it connected to iTunes it did a Restore as above.
- It took about an hour to restore. And even longer to download all my apps.