Nice to see you back Gattina. Here's a bit of a list but some might be a bit Spring like for your garden:
Fuchsia, forget me not, Jacobs ladder, Solomon seal, anemone blanda blue, viola, begonia, lobelia, browallia and brunfelsis paciflora are some I've seen pictures of. They all say they are shade tolerant.

Hello, Cammomile! Thank you for all those suggestions. I don't know either Browallia or or Brunfelsis, and had completely forgotten about Violas: I'm so used to thinking of pansies as Winter/Spring colour that I tend to forget their little sisters. I sent off for some scented Begonia corms, and have been very disappointed with what came back. They were the smallest I have ever seen, and not a single one has started into growth yet. Keep your fingers crossed for some fuchsias I have. Begonia! That's probably my best bet. Again, thank you.