My Task Host problem has now gone and it may or may not be linked to the change I made yesterday when I turned my Memory Integrity on. For some reason it had been off.
Windows Security – Device Security – Core Isolation – Memory Integrity. I had to restart my PC, which took ages (about an hour) but it was worth it. On restarting, Windows Updates started working again, albeit slowly. At the moment, things are more or less back to how it was before Task Host began playing up.