I presume you mean Asclepias incarnata 'Ice Ballet'. which is Swamp Milkweed.
Since all of these died of cold here, I doubt if it is going to be invasive in Lancashire.

Thanks Owdboggy. I've planted a couple of plants recently that have turned out to be a nuisance as they are invasive and now can't get rid of them !! So just needed to check this one out.

Join the club! We grow two types of plants here, thugs and dying!