Many thanks to all for your interest and I can only apologise for the fact that despite having not done anything suddenly I can now contact Google. There has been no change to their certificate and it is still as described so it will probably go wrong again as soon as I finish this post.
In the meantime here are some answers to the questions
1.Time and date in synch
2. I was using google search in Firefox.
3. Can't comment at the moment.
4. Firefox 34.0.5.
5. IE and Yahoo search gave same result...could not contact google
6. This is a new laptop and I have been using google search to clear out bloatware.
Not on any network
The certificate was issued by UTN-USERFirst-Hardware and on closer inspection there were some some strange things ...organisation "Google Ltd Tech Dept" and it expired 14.3.2014. This doesn't seem right but everything seems to be working at the minute so....