You can cut off the flowered stems from your bluebells but if you cut the leaves off you will affect next years flowers.
If your beets have been well hardened off they should be fine to plant out. They can be sown outside earlier than this so no worries.
Leeks are pretty hardy. I grow Musselborough which stand in the garden all winter, so yes, plant them out..

My beetroots are doing great - no slugs. Yes, by all means, plant out your beetroot and your leeks. There is time for them to get big & fat. Beets don't like the hot summer so try to harvest them by July 1. You can plant another crop end of August.

If the bluebells are still green, I would leave them be. They are still photosynthesizing and building up energy for next year. Trim them when the leaves turn yellow and are fallen.

Thanks for all my answers, helped me a lot . Did plant Beetroot & Leeks today .Have put ‘Clotches ‘ over them ,to stop birds pecking them .

Those birds are a pain. I can hear the mockingbird laughing when he sees me planting more seeds - again!