Thanks for the point PJ. I note that I last posted just after 5.00pm GMT and I have not seen Carnut's post at 5.20pm - so that must be about the time I lost my WiFi connection. I have been unable to use the internet all that time until now.
Very frustrating, and I didn't really deserve the point, because you made it quite clear that the solver would have to answer correctly all your questions. Once again, thanks.