They are pronounced CORDYLINES and yes of course there are plenty that have survived the past 2 cold winters.

It's going to depend a lot on where they're sited because one that's in a frost pocket or a very exposed site will struggle whereas another in the same street might come through unscathed.

Cut your plant down to the ground if it's been affected and see if there's still life in the roots - if there is it'll send up new stems/growth.

Mushybanna posted a picture very recently of shoots coming up from a damaged cordyline. There's one here -
http://67.207.144.157/photo/slideshow/202830-life-after-death/member/mushybanna

Don't dig it out yet Simon!

And I dug out one planted last year, only to discover it was putting out new growth at the top of the rootball which I couldn't see before taking it out. Another week and I'd have noticed it...

it also depends how well established they are as that seams the case hear in sunny norfolk and makessome sense .

I have a red cordyline that I put in a well protected border. It died a couple of years ago, but then last year new shoots emerged. I was sure it was killed off in the last winter, but sure enough it is producing new shoots once again.