I was listening to one women say she had lost about £41/42,000 because she receive state pension at 65 instead of 60.
The woman likely calculated her loss by estimating the amount she would have received if she had started receiving her state pension at age 60 instead of age 65. This would typically involve multiplying the annual pension amount by the number of years she missed out on receiving payments (in this case, five years), potentially factoring in any increases in pension amounts due to inflation or changes in pension rates over that period. The figure of £41,000 to £42,000 could reflect the total of these missed payments.
However this doesn’t take any account of the higher pension she has been, and will continue, receiving. I can just about see there may be a legal case for people not being notified but I would have thought that proving you didn't receive something would be very difficult.