Check for signs of new growth at the very top - if none, you can try cutting the plant down by half if you want, or just give in and dig it out.

I have now cut it as far down as I can, but the remaining stump of around 10inchs smells awful, I cannot dig it up as the roots have firmly set. Does it sound like it has died?

Awful smells usually mean rot has set in. Oh dear! I hope the nurseries have lots of supplies of cordylines as many have died over this winter. Maybe now they will stop telling us we will have a Mediterranean climate!!