As long as there's no frost or the ground's not waterlogged, yes now is a good time.

once dug out you can turn the soil and prepare it ready for planting their replacements. but not if frozen.

I would add in feed into the planting spot. Lavender like poor well drained soil. Box likes rich dampish soil. I like to use chicken pellets for green growth along with fresh compost.

Thanks for advice will start at wknd ?