Not sure bluebells or any wild flowers would be happy underneath leylandii, or any other conifers for that matter. They prefer better lit areas, plus any conifer that drops leaves or needles over time tend to smother the ground, and make it acidic. Certainly woods where bluebells grow widely in my experience always have mostly deciduous trees, and the bluebells are normally starting to flower around the time leaves are really starting to come out properly. Visit any majority coniferous woodland or forest, and the ground will have virtually nothing growing beneath the trees.
I’ve been largely letting most of my garden look after itself, I’ve got violets growing everywhere, snowdrops are spreading, cowslips are popping up everywhere, including between the patio slabs, more and more primroses, snake-head fritillaries are now flowering, as are celandines, bluebells are in leaf, and I’ve got some wood anemones flowering in a planter, which I’ll put below my silver birch. Some things are spreading into the lawn, and I’ve been collecting wild seeds that I’m going to scatter across the lawn, and I’m getting a load of yellow rattle to spread across the lawn as well, which will parasitise on the grass, keep it under control and let the wild flowers spread without getting swamped.
I’ve got a packet of nematode worms to spread around the garden, to deal with the slugs and snails, which leaves the cats that shit on my lawn, and have been scraping up the compost in the big pot my apple tree is in, and shitting in there, which is just disgusting.
The branches I trimmed off the gorse bush at the bottom of the garden and spread around the top of the pot I’m hoping will act as a deterrent, though… 😈