"More than one contributor stated that aerobatics were prohibited in a Cessna 172. Well, on all of the Cessna 172 limitation placards I have read recently, the only thing which Cessna chose to specifically prohibit are intentional spins with flaps extended, and use of full control inputs at speeds greater than a certain value (depended upon year and units of measure)."
The fact is that the flight manual is part of the C of A and flight outside it is illegal. There is no difference between 'not approved for aerobatics' and 'flight into known icing conditions prohibited' as far as whether they are allowed or not.
There are differences either side of the Atlantic about what constitutes aerobatic flight between FAR and CAA regulations. We do not define aerobatics by reference to any particular pitch or bank angle and my understanding is that the FAA do.
If the aeroplane has British registration then CAA rules apply and any flight within the FAA definition but outside the CAA definition of aerobatics is permitted.
This is what matters not whether a pilot may get away with any particular act without the machine disintergrating or becoming irrecoverable.