Posted: 14/04/2016 at 09:43
Unless the border will be to the north of the yew hedge I can't see a problem. Christopher Lloyd's wonderful garden at Gt Dixter is chock-a-block with yew hedges with wonderful borders in front of them.
Of course the bed needs to be nice and deep and regularly fed and mulched, with lots of room so that your shrubs and perennials aren't actually growing 'under' the hedge ... but you've said it's a large border so all should be fine. It sounds really appropriate for the setting. I'd love to see photos - very jealous of a walled garden!