It's really a matter of aesthetics, whichever look you prefer. Either way won't affect the bush now that it's dormant. I leave the flower heads on for winter interest but clean it up in the spring before it's starts to shoot again.

Thanks, Bathgate. Oh yeah! a Merry Christmas.

Thank you Treetop! Merry Christmas to you and yours too!

It is usual to leave the flower heads on as Bathgate says. It also gives some protection from frost to the first buds. they are usually the ones with next years flowers in them. They can look pretty with a hoare frost on them.

Yes, usual advice in the UK is to trim off the dead heads and any dead bits after growth has started in spring.

Thanks guys/girls, your advice is much appreciated.