Ground cover for shade that will stay put?

[WhatToWearFor8b]

I've got a terraced garden. The bottom terrace is in the shade of a big matipo (evergreen but lets some light through, relatively high canopy). It's also got the trampoline on it, so more shade from that. Soil is alkaline and not as dry as you might think (it's at the bottom of the slope of my garden)

That terrace is bounded on three sides by paths / retaining wall. Then on the fourth side, there are sleepers about 70cm or so high, which retain my grass (by which I mean dandelions, Spanish bluebells, creeping buttercup etc etc).

I'd like to plant something in the shade but don't hugely want to add to the woes of my grass!

So, will lily of the valley invade up the hill to my grass? Or will the sleepers and change in level stop it? Any other ideas?

Oops name change fail! That pseudonym is a bit less relevant for this thread than it was for the one I created it for!

Epimediums are lovely and not too invasive, and there are loads of geraniums that tolerate shade. Lily-of-the-valley are buggers for spreading but a change in level and the physical barrier of the sleepers should contain them.