Plants for gravel area

I have a gravel area that is planted with various Verbenas and Echinops. There's an area by the summerhouse that doesn't get much direct sun this time of year where I had some Astilbes for several years. I've removed them as I was having to water them a lot, but can't find anything to replace them with.

Could anyone suggest a perennial that grows to 18-24 inches, doesn't need watering a lot and doesn't need full sun? Also, it should be immune to slugs.

 

Sesleria autumnalis is a mound shaped evergreen grass which will tolerate dry stony soil, as in its native habitat. It grows to 40-60cm and has attractive white flowers, growing in sun or shade. I have three in an east facing border, untouched by slugs or snails .

 

Thank you very much. This sounds excellent. I'd forgotten about trying grasses.

 

Some Achilleas don't mind less sun at this time of year and many Asters as well, although my Asters were destroyed by slugs this year - they aren't usually bothered. Aquilegias will also be fine, although they can get a bit of mildew, especially as they fade.
All the 'A's

 

I have dryopteris ferns, Brunnera, hardy geraniums and Epimediums in that sort of place. Aquilegias too and if they get mouldy I cut them down and new leaves grow.