Which way is it facing Dan, North South etc, maybe a fern, sounds quite woodlandy with the plants you've chosen, hardy geranium I have sylvaticum Album which isn't too tall and there's Astilbes with their feathery foliage would maybe contrast with the bergenia? and astrantia but they do have similar foliage. Day lily but they can grow quite big :-)

I have a daylily in the original part of the border. There's one damp patch where the drain pipe drips from the Wendy house so possibly an astilbe for there :)

Catalogues like Suttons are handy for this sort of question because they have little symbols for how much sun/shade the plants like. I was quite surprised by how many are tolerant of some shade.
One point though - if you have a day lily perhaps choose something with a totally contrasting leaf shape to go near it.

Yes! I the day lily I have now is between an aquilegia, hydrangea, agapanthus and a bergenia :)

So how about a fern and either a Brunnera or a Pulmonaria for the shaded parts? Nice contrast of leaf shapes with what you have already and both nicely at ground level. Or perhaps one or two perennial geraniums? And a geranium sanguinium for the very front in the sunniest bit?

They sound lovely! I'll look into them today :) will be off to the local nursery too to see what delights they have :) Thankyou all for your advice/suggestions it's much appreciated :)

If you can't find the G sanguinium I can send you a bit.