Many thanks for your considered reply.
Attempting to follow your instructions:
Unable to temporarily disable Perfect Disc, no such option found.
As an alternative & because I strongly suspected Perfect Disc anyway I uninstalled it.
Result was an immediate improvement in CPU & Memory.
Down initially from CPU spikes at 100% & Memory at about 1.8Gb down from about 2.8Gb.
Checked (again) Wauaserv, No evidence on any instance of Svchost.
Windows update history checked & some failures seen, but all eventually recorded as completed.
Next checked my hard drives, one is known already to be suspect, but rarely used for a year or so now except for unimportant data.
Your HD Checker downloaded & reported all HD's as "passed for overall health". some errors recorded on the suspect HD.
Then checked my SSD with the Transcent custom checked, All OK there.
I have Crystal Disc installled so checked with that also.
Again all reported as "Healthy" status & all "Stable" > 98%. The suspect HD recorded about 650 reallocated sectors while reading as Stable, I don't think this has changed on over a year.
I am about to restart & check CPU/Memory because this is when formerly I would see the masssive useage which did reduce over many hours.
Well restart failed, but after about 1/2 hour I was able to restart. SVChost is now running at about 50% of CPU (reported By Process Explorer but not seen in Task manager)). Total memory use about 3BG (Task manager).
I am baffled by all this........................