I'd leave it alone right now - frost can sometimes cause damage, and having the flower heads still present helps to protect the plant. Wait till late April/early May and cut them out then, when you can also remove any unwanted growth generally.

I have 2 which are very big and over 12 years old and every year I leave the tops on, the frosts turn them black but I never cut them off as I think this still gives them some protection.

thank you bamboo and drc726 for your anwers, we will leave well alone until later in Spring.

There is a vigorous FJ right nextdoor to us. It has very late flowers with loads of nectar that attract insects till very late in the year. At the moment it has small green berries about 8 foot above the ground. Mahonia is the same puzzle. Early/late blooms, then berries that birds go mad for in the summer. If I chop the tops off too early the birds lose out. So I do it after that. I try to be bird and insect friendly where possible.