These are:
A - Scrap
B - Break
S - Structural
N - Non-Structural
There is a lot of detail in the new code of practice how a damaged vehicle will be placed in one of these categories but crucially there is now a clause in the code specifically for historic and classic cars as follows:
9.4 Historic / Classic Vehicles
It is recognised that some historic/ classic vehicles or vehicles of special interest may be repaired irrespective of extent of damage, providing it is safe to do so. In these cases the vehicle will fall outside the Code of Practice, which will not apply.