I live in Oregon, on the west coast in the US, where we do get dry for 3 whole months, so woodruff is considered a woodland plant, so if yours does do well in the sun, a number of woodies would do well.
Interesting to learn that it grows in the shade! All the patches in my garden are in full sun. Maybe that's why other things are competing quite well. I have magnolia in one patch, potentilla in another, and a patch of irises amongst the woodruff. It does seem to have spread madly last autumn/winter though, so I will be digging it out from around the crocuses and things. The hardy geraniums keep on top of it and nothing seems to stop the muscari (grape hyacinth).
I imagine you are talking of shade, since sweet woodruff grows in the shade. Try phlox paniculata' David, it is woody enough to come through, other small leafy types might get overwhelmed, Kirngeshoma palmata might make it through, I know hellebores come through ivy and so does polygonatum hybridum, disporum and hardy fuchsia. Well gardening is all about trial and error. Good luck