You probably have all this information from when you visited, Eve, but just in case!!!!!!
The original cathedral Organ was built by William Hill and Sons in 1882, the current organ was installed in 1927. Major restoration work was undertaken in the 1980's and eleven new ranks were added, including a fanfare trumpet. The Cathedral organ is one of the best romantic instruments of its kind in the southern hemisphere. Taken from the Cathedral website: http://www.christchurchcathedral.co.nz/discover/cathedral_history.html