Unless my memory fails me, the COS99 -> COS08 was a choice. Those that stayed on 08 made the choice, the Government has already come to the party WRT discrimination, they won't be giving you a second chance. You decided to keep your 55 retirement age, there is no discrimination.
Now if the company starts running out of pilots due to those retiring at 55, you can absolutely bet that you will be given another chance to extend your retirement age to 65+, but do you think it will be on your current terms? Absolutely it will be C scale but more likely by that time it will be D scale. There will be no cake and crumbs in this one.
We all made a choice that we will live with, there is no discrimination in you choosing to retire at 55.
Just my crystal ball.