Try reading the original post again.
Neither the CAA nor the training organisation bears any legal responsibility in the case quoted.
That is not clear to me. If the OP was training at a school, and booked a test with the school, and the school supplied the examiner, then the school has a responsibility to check the examiner's dates just as they check their instructors' dates.
The school can't say "you ordered an examiner, we contracted to supply an examiner, but actually we supplied someone who wasn't an examiner, but somehow that's not our problem"!!