Over-wintering echiums

I've got half a dozen E candicans (I think, some of the labels washed off) that I've got to get through the winter somehow. I've planted most of them in the garden but still have a few I could pot up into bigger pots for the winter.

How sensitive are these going to be to the cold and damp? I have E wildprettii once and they made it through to February and then collapsed.

Will I have to make some sort of cover for them?

 

E candicans is in my opinion more tender than E pininana, which stands a chance in mild winters.
Never got candicans or wildpretii through a winter outside, but only tried both once.