In reply to shaned:
Most locals don't climb much in winter..but coming from the UK it wont be any problem
In the southern lakes district all the north facing crags at Wanaka and Wye creek are awesome on a sunny day. the southfacing crags will be damp.
There will be good skiing, and Ice climbing in August.
All the climbing over about 1200m will be in snow so No alpine rock in Queenstown, darrens, or Mt somers.
Babylon at milford faces north and is at low elevation so may be alright.
bouldering at castle hill and Jardines will be fine on the sunny sides and suprisingly we get a fair amount of sun in winter. It is possible you will get a little snow.
There is a guide book called south Island rock that is quite good for travelling.