Mine grow about 4" a year, perhaps a bit more.
Not sure they are the best choice for a woodland floor. Had you thought about Butchers Broom?

Sorry Steragram, I disagree.

It would grow a tad slower than full sun, but otherwise would be fine.

- I grew one in previous garden that was up against a south fence (on the north side), had a rose along said fence that gobbled up any available light and smothered the wooden boards. Not only that, a Viburnum carlesii grew over the Box and embraced it within a grotto of thick foliage. - A quick mention for the gorgeous scent of V.carlesii.

All in all, it (Buxus semp.) did alright for itself.

Only going on what mine do Fractal - but if yours are more vigorous, then why not go for it anyway.

Good for wood unless you have box blight nearby. Agree the Butcher's Broom (Ruscus aculeatus) would be good and is native to the UK. Other's could be the ground cover Mahonia (winter flowers gd for wildlife) many varieties of Euphorbia and Sarcococca.

Didn't know there is a ground cover Mahonia - do you know the variety Hoya?