Welcome to GOY. What about a hit and miss fence. Posts are sunk in the ground then the slats are put on alternative sides but overlapping slightly so that you cannot see out or in but the light can still get through. The hedge could be allowed to grow through it or you grow clematis or roses against it. If you can get a hold of some of the upright branches you could try layering them - running them along the length of the hedge. The branch will then put out new shoots growing up which will fill the gaps. I would not advise you to use solid panels because you could make the hedge unsightly. I will put a photo in my site to show what we did. I'm sure you will be offered other suggestions as there are some pretty good gardeners on here.