Primarily you need to wait for the soil to be a bit warmer, mostly from a replanting point of view. Best if the soil is not frozen, even if you're transferring to pots, nor waterlogged. March would be the optimum time, so long as its not unusually cold, in which case, April. That said, I have stripped out an entire bed of permanent planting and transported the contents elsewhere and replanted in mid February - but I'm in London, and it was an unusually mild February. If you can see weed germination, or seedlings, popping up in your borders, that means the soil is starting to warm, and it can be done then.

With regard to the bronze fennel, if you can get that out intact, you're a better man than me gunga din - after attempting it years ago, I discovered the tap root goes down an awfully long way, and I've never managed to move one that's been in situ for longer than a couple of years successfully, but they're not expensive to replace anyway.

I agree with bamboo. having said that I am removing couch grass from a border [when the sil isn't frozen] and the plants get lifted, checked for couch grass, re-potted and put in the greenhouse. they will go back in the border when it is all dug out and settled in the spring.
obviously in pots keep and eye on the watering.

Thank you Bamboo and Seaburngirl. I will wait untill March/April depending on the weather.