So i'll read it for you how about that.

Minor changes to wheels
Wheels up to 26mm wider than the largest optional wheel recommended by the vehicle manufacturer for the
vehicle can be fitted without the need to notify the RTA.
The outside diameter of the wheel and tyre combination must be no more than 15mm over the largest diameter
wheel and tyre combination specified for the vehicle and not more than 15mm below the smallest diameter wheel
and tyre combination specified for the vehicle.
In plain english get whatever size you want just ensure outside diameter is 15mm more then the original outside diameter.

So to do this you get lower profile tires if you want bigger rims. However legally you have to have the same tyre load rating as stock too.

it wouldn't be a wheel tyre thread without the age old website.

http://www.1010tires.com/tiresizecalculator.asp