@nimbuscloud oh, i love peonies but my only attempt to grow them ended in disaster... perhaps i should try again!
@Oenanthe i shall add sedum to my list to try... we have plagues of slugs and snails that eat everything, including things thay should be slug proof...pulmonaria, astrantia. We have v damp soil though, so not sure where I'd put them.
Lots of other suggestions that i would agree with! We had a lot more in our previous garden which i loved (jasmine, wisteria, echinacea, erigeron, verbena) but I'm not sure would work here... that garden was hot, sunny and sandy... now we are wet, shady, clay! Geums i am trying for the first time, and so far they are doing really well.
Also a couple i forgot for stature in the shade are fatsia and mahonia.
@Atalune Japanese anemones flower later in the year. My foliage is currently about a foot high, but they should be sprouting quickly now. Hope they come good for you! Lemon balm is lovely but does indeed spread a lot! Maybe i should add some, we had a big clump in our previous garden.
@girlonamission oh, agapanthus is a good one, i have a lovely big pot of that! The clematis i have not had much luck with as something, presumably slugs or snails, always eat the growing tips.