snip

sized boundary.

If you've no objection to using glyphosate ("Roundup" etc), it won't
do the slightest harm to the hedge

Actually it will, especially if you times your idiotic advice by the
thousands of people who also naively rely on such toxic chemicals,
usually thinking advice from the village idiot is OK.

You can download "Glyphosate.pdf" from their website at
www.pesticide.org

As I have a similar problem I would be interested to know what harm
would the careful application of glyphosate do to the hedge if the user
is careful to ensure that no drift or overspray occurs.

Just times the careful use by the many thousands of people here using
it and you have a huge problem.

My question was whether or not it would do any harm to the hedge in my
garden.

--
rbel