Don't think this is true for the GU either as I believe the standard OEM tyre size is a 275/65/R17 (785 OD).
That would make the 285/75/R16 (833 OD +48)
The 265/75/R16 All Terrain (803 OD) +18
The 265/75/R16 Mud terrain (813 OD) +28
* based on Cooper Tyre sizes. Varies slightly between brands and tread depth.
Theoretically even the 265/75/R16 would be illegal (greater than +15) if the cops pulled you over in the first few thousand Kms. Most Cops though doesn't seem to pull you over for anything smaller than a 35".
However as always it is your insurance company that will sting you. They are not required to pay out on vehicles found to be "defective" or "un-roadworthy". So you may find yourself up for the expenses of all parties involved.
I have heard of some people being stung even when they didn't think they were at fault as the insurance company could prove the mods reduced the vehicle ability to stop/avoid the incident.
Just check it out before you go ahead with purchases. Tyre placard is in the glove box.
Happy to be corrected with other figures if people have them.