How hardy is chasmanthe floribunda - ie can it safely overwinter in the soil in Northern England?

It is not hardy being a S.A. native, unless you have some way of protecting in winter I would say no.

I thinkyou'll have to dig it up, pot it and keep it somewhere cool for next year. Lovely plant...why are these things never hardy!!!

I had been lead to believe it was hardy so i left them in the ground. guess what? they were not so i lost them :o( if i ever grow them agian they will be in pots so they can go in the greenhouse.

Wow, spectacular plants though. Might have a go with a few myself!