You will already know about deterring slugs with eggshells but have you ever tried using garlic powder?
Sprinkle a generous scattering of garlic powder around your vulnerable seedlings - the resulting aroma really effectively deters slugs and snails (and even young-shoot-gobbling pigeons too!)
I re-apply the garlic powder every 2 weeks or so. The smell lingers even after heavy rain, so don't worry about the garlic powder being washed away. Try to aim around the plants when scattering (although they don't seem to mind the garlic powder landing on their leaves).
You could probably just use garlic powder, but I like adding washed-clean - to avoid encouraging vermin - and 45 minute-or-so oven-baked (when the oven is already on) - for extra crunch - eggshells around the base of seedlings. The (circa 1cm x 1cm) fragments are unpleasant to crawl over (further deterring pests) plus the eggshells will eventually break down, adding nutrients to the soil.
We can all have slug-pellet-free gardens AND safe plants now - hurrah!