It happened to me last year, so at the end of the season I loaded all the tops up and took them to the recycling place. Apparently their composting machines run so hot it kills the spores. My composting skills have never been my strong point ;D
All the best
Sue
PS you are certain it is blight and not a bit of frost damage (hope I am not speaking out of turn to an expert here -especially from your avatar, but forgive me if I am as I am new to the forum)