HeaderFooter and table formatting

Hi there, I have successfully created a pdf with some tables and decided to add a header and footer to the document.

The problem is that when I add the header, the formatting of the table contents becomes out of sync with the table borders - it appears that the header text pushes the table text down the page. Here is the working page without header (the table overlaps two pages):

And here it is with the header:

Any ideas? Thanks, Dominic

p.s. sry if this has been asked before, I could not find a similar question