Just a quick note from a kiwi climber based in Christchurch.
All the info you've been given and that you have sourced to date is right on the button, theres really not too much more you need to know. Its a good move to fly into Christchurch and bus/ hitch from here. A car is nice if you want to climb anywhere other than Paynes but not essential if you don't mind a bit of grief hitching to the seaside crags.
Would offer to run you up to Castle hill for a day or two but I'll be in the Blue Mountains for a couple of weeks by the time you get here.
Enjoy your stay.