your minimum ground clearence has to be 100mm.
It is a legit defect if your wheels scrub on any part of the car.
the wheel one is a little more complicated.. Your wheel and tyre combination must not be more than 24mm total diameter larger than the largest wheel and tyre combo that came standard on that car so if it came stock with 17" rims and big tyres then if you put 19" rims with tiny low profile tyres on it then it should be about the same size.
just stand the wheels with tyres fitted side by side and if there is less than 24mm difference then they are legal.
this is stated in the "light vehicle code of practice" you can get a copy through the RTA technical advisers but it may cost you.
hope this helps.
Cheers,
Kurt.