Easa ?
This 12 year thing has only appered since EASA came into being and is because of the differences in interpritation of "public transport".
In most of continental Europe A public transport C of A is only required for work that requires an AOC, in the UK a public transport C of A is required for anything except srictly private flying.
This means that Flying training (for instance) requirs a public transport C of A in the UK But this is not required in the rest of europe.
The problem is that there is no joined up thinking at the CAA and rather than change all the rules at the same time the maintenance part of the CAA is embracing the EASA rules but the rest of the CAA seems to be in a time warp and has yet to change the rules to enable flying training to be carried out without a PT C of A.
When C of A is next renewed on your aircraft there will be no private or PT clasification it will be just a C of A and it will be up to the opperator to ensure that the maintenance conforms to the requirments of private or PT use of the aircraft.
The whole thing is a mess and shows that the CAA simply fails to understand the effects that the rule changes have on the industry that it (miss)regulates and for this stupidty we now have to pay charges that have increased far above the rate of inflation.