If flowers are too much hassle and time is limited, how about just laying trails of holly and ivy along the centre of the table? There's a bumper crop of all the berried foliages this year including mistletoe. So even if you don't have any growing in your own garden, there's bound to be some in the hedgerows to forage whilst walking the dog or in the park. Alternatively what about just tying a sprig of something (not too prickly!) to the napkins with a bit of present wrapping ribbon?