One that does quite well for me in shady places is Bats-in-the-Belfry, a native campanula that does well on clay.
http://www.bbc.co.uk/gardening/plant...ges/4747.shtml
My favourite is cat's ear. Grows well, has a good balance of minerals, not a pest plant in the UK. Tortoises really like it. I let this plant seed everywhere.
http://wildflowerfinder.org.uk/Flowe...ar/Catsear.htm