Thank you for your comments. I am using what I believe is that latest Kindle (bought November last year) - not the 3G version, though.
I have tried using the free Kindle file conversion service but in every case the file that came back had the first page of the article omitted: I did raise the issue with Amazon but got no response.
A problem is that I am visually disabled and therefore I can find it difficult to work around websites when the text is not a good colour to contrast with the background. However, after searching the online "help" for Calibre I found nothing that seemed to relate to this problem: and there seems to be no link to contact Calibre themselves for assistance.