Hello Malcolm,
I am sorry to hear that your computer crashed after AVG update. Please press and hold the power button for 20 seconds and try to force restart your computer and check if you are able to login to windows. If the issue persists, please follow the steps from this link(http://avgclick.me/rebootintosafemode) and restart your computer in safe mode with networking. Please let us know if you are able to boot your computer in to safe mode with networking.
Having followed the updating procedure and re starting all I get is a black screen and no Windows 10 to be able to do anything.
Hello Malcolm,
I am sorry to hear that your computer crashed after AVG update. Please press and hold the power button for 20 seconds and try to force restart your computer and check if you are able to login to windows. If the issue persists, please follow the steps from this link(http://avgclick.me/rebootintosafemode) and restart your computer in safe mode with networking. Please let us know if you are able to boot your computer in to safe mode with networking.