Hemitelia smithii - a Hardy Tree Fern?

A number of years ago I purchased spores of a New Zealand tree fern, listed as 'Hemitelia smithii' in the Chiltern Seeds catalogue. (not currently in their online catalogue). These did produce a number of small plants but most of them subsequently died. I was eventually left with 2 fairly vigorous plants which are located in the back garden and have survived frosts down to -7°C. The fern pictured below is now big enough to begin forming a trunk.

There is very little on the internet about Hemitelia smithii and what there is suggests that it may in fact be properly named as Cyathea smithii.