Groundcover for an Impossible Area

This photo shows a short walkway (about 25 feet, so maybe not so short) at the Big House, that breaks up what would otherwise be a pretty major hill or flight of stairs to get from one area of the grounds to another.  It only gets "windows" of sun, but when the sun hits, it is blistering!

For two years I looked at struggling espaliered Camellia japonica, underplanted with vinca.  It simply never looked good.  I think I've hit on a good combination for this area, even though all of the "experts" say it shouldn't work well here.  It is heavy clay soil, with major amounts of lime that leach into the soil from the brick wall footings.  In any case, for me it's working, and you should feel free to steal the idea. 

We planted Rose "Sombreil" along the trellis, and underplanted it with prostrate rosemary.  Both are loving life in this spot, and the combination of the two distinct fragrances is awesome!