A small update. It seems that the above explanation may not be entirely accurate and that there may indeed be some posts that are on the next page.
Could I please ask you all to do something for me to check what they are telling me?
If you see a phantom page, then before you post a reply could you please make note of the last post number and the post content on the last page visible. Then when you have posted please note if there are other posts already on the new page.
Not sure if that will help them but it would help me.
Many thanks.