Not knowing why you asked the question I'm not sure how to answer. Is there are problem with them? Are they too big for where they are?

I think you are talking about overwintering, or whether they will survive the winter? In Kent you should be perfectly ok. The dry seedheads will self seed and treat the main plants like a perennial, cut them back when they die off and hopefully they will re-grow next year. When I lived in Nottinghamshire, mine never survived the Winter, too cold, but now I'm on the Isle of Wight I don't have to worry about them at all. You could shake the seedheads into a paper bag and seed them yourself for an insurance policy.

Thankyou both for the replies. They are still in flower at the moment so are ok , but just wondered whether I had to do anything to them when the flowers eventually die off.

Sorry I misunderstood the question Jay

I have decided not to cut mine down as there were 6 or 7 bluetits pecking away at them this morning, whether for insects or seeds I couldn't tell.
I'm leaving most of the perennial seed heads on this year in the hope of helping the birds, and will cut them down in Spring.