It looks like case closed - I picked up a Blackberry last week & installed the software to backup the phone. Now within that package & unannounced to boot is Macrovision software updater, a wholly unnecessary piece of kit.
Looking in Msconfig shows Isuspm.exe which is the update scheduler. I've stopped this from running at startup & everything is back to normal. Strange that it didn't appear in resource monitor as a resource hog & it also has no uninstaller, not does it appear in the list of installed programs.
There's some removing to be done.