No not dying Winnington. Tie those Fronds up and stuff the crown with fleece and put it somewhere frost free..

What genus and species is it? If you are talking about a New Zealand tree fern, they mostly seem to be Cyathea though there is Dicksonia squarrosa.

Is it in the ground or in a pot? Dicksonia Antarctica do need protection as ydd says in this country, however I have seen many survive without. As long as the crown is kept dry, there will be no chance of the inside where the new fronds come from freezing, that is what will kill your tree. The fronds go brown this time of year as it is coming to the end of its season. Cut them off and that is what forms the large fluffy trunk overtime. The new ones will start to appear next year when the weather gets warmer. Stick your fingers in the inside of the crown next year and have a feel.