Can't name the plant, although I do recognise it. As for the bluebells - could you give some away to friends or donate them to a local park/woodland?

Thanks. I am wary of planting bluebells in the wild as I wouldn't want to impact feral bluebells, as has happened with daffodils in the Lake District where tourists have planted daffodils. No-one asked has expressed interest in having bluebell bulbs.

I'm afraid the only answer with bluebells is to dig them up, making sure you extract any and all bulbs. Agent orange might work on them, but then you wouldn't be able to grow anything else, and they remain untouched by the more usual weedkillers.
The plant in the picture is very familiar, yet I'm also struggling to think what it is...

Is the plant possibly the wild Astilbe, Meadowsweet? The leaves do have that Astilbe look about them.

Looks like Astilbe.

Thanks to all for thoughts. I have looked at web photographs of Astilbe and the leaves seem to fit although the stems on mine are red while those photographs seen were all green. The flowers will no doubt confirm if it is an Astilbe in due course.

I never thought of meadowsweet as being an astilbe, Ojibway, but of course. If this was a deliberate wild garden then meadowsweet could have been planted.

Maybe one of the very many eupatorium (joe pye weed)

Joe Pye Weed sounds like it will spread if kept in the garden. Perhaps in the meantime I will keep the plant in a pot and see what develops and I can get a clearer idea of what it is. If an Astilbe, all well and good, otherwise...
Thanks to all for comments.