Posted: 09/08/2015 at 21:23
I should have thought loads of plants would cope there, especially if this autumn you can pile on a thick layer of mulch such as well rotted garden compost or maybe some cheap potting compost bought at the end of the season. This will be worked in by the worms over winter and will improve aeration and moisture levels.
Dig out some of the montbretia/crocosmia first if you can as it will spread further if you let it.
In the mean time, have a look at achillea - loads of colours - aquilegias - again, loads of colours - shasta daisies, Japanese anemones, roses, physostegia, veronicas, phlomis, hardy geraniums, lysimachia alba clethroides, phlox, hemerocallis, echinaceas (slug magnets) lychnis chalcedonica, peonies, persicaria.
That should be a good start and cover lots of shapes and sizes of plant and their foliage forms and flower colours.