Thank-you all for your responses. I have followed the suggestions. The laptop appears to be behaving better. I will post any happenings here. Particularly after Patch Tuesday. Are the Avast Makers considering putting in a default wait before it goes to the web to check for updates? I fully understand that you can't be solving problems caused by others, but as a user, it would have been really helpful. I had to uninstall about 8 applications to figurew out there was a clash.
Once again, thanks for all your help!
Ludo