I initially pointed Big Screen EPG to the new url but it couldn't parse the file. To get the file uncompressed you need two freeware programmes, Wget and Gzip available here: http://www.gzip.org/ and here: http://users.ugent.be/~bpuype/wget/.
I put these files in a directory and used this batch file as an automated task to download and unzip the epg file:
wget -N http://nzepg.org/freeview.xml.gz
gzip -d freeview.xml.gz
Pretty simple but now Big screen epg can read the file. Hopes this helps someone...