1803 + avast. Unable to get any internet access via wifi or ethernet - issue was that no IP addresses were being assigned (DNS issue?) - resetting internet parameters, rebooting , reinstalling network drivers all failed. Uninstalled Avast - problem disappears as soon as Avast Antivirus was uninstalled.
Reinstalled Avast all fine till next boot. Now we have internet connections.but all UR:s are invalid.
Seems to me that Avast is still unable to interface with Windows 10 properly - best to avoid for now.