ang is correct if the garage is accessed through the dwelling.....
im assuming it will be accessed independant of the dwelling????
a garage is exempt from permission if it is:
1. under 25sq m (269 sq ft)
2. finished to match the dwelling
3. not placed forward of the front wall of the dwelling
4. does not reduce private open space to less than 25 sq m
height does not exceed restrictions (4 m pitched, 3 m other)
5. is not used for residetial, agricultural or commercial uses....
therefore from what you have described, it does not require permission....