If I take the watermark off the page, then I can do as you suggest.

Formatting the para mark immediately below the table makes no difference and once the w/m is applied - the bottom table cell row drops.

Taking the w/m off again, and doing the same with the header & footer as suggested, then this immediately drops the cell row even before adding a w/m. This seems strange (header & footer), I would have thought it would have had the opposite effect?