Something that looks bold and lush, to counter the small-leaved spikiness of the mp. How about hostas, fatsias, bergenias? Certainly bergs and spring bulbs go well together anyway, and bergs and fatsias would give structure and colour in the winter too.

Or as the mp has a formal air about it, carpet bedding could look stunning.

I would go with Euphorbia Fireglow

It would look stunning , what ever you choose I would keep to the one variety rather than a mishmash of odds and sods

Gg

and don't forget to water it very well as the bedding will take up a lot of water from the roots of the tree.

how about pulmonaria as they have good foliage too.