one of my neighbours had the same thing, so i told him to cut it back to near ground level, it's already sprouting nicely..

Well, sort of. Usually, a Cordyline damaged by the winter last year would by now have shown signs of new growth, often from the base where the roots are, or sometimes up the old trunk, if there is one. If your Cordylines have shown no growth at all this season, they're very likely completely dead and should be removed. If there is new growth, the time to have cut back would have been late spring/early summer, at least by June, so if there is new growth, and the trunks are rotting or smelly, cut them down - if the trunks are ok except dead, leave till next spring.