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....
The school cannot 'supply' an examiner - it is not a commodity that it controls. The examiner authority is issued by the CAA to an individual who, when exercising the privileges conferred, then acts as an agent of the Authority. The school has provided the contracted service when the training is complete and a recommendation for test has been made iaw JAR-FCL 1.080(e). Whilst it may offer to assist the candidate in finding an examiner, the school has no legal responsibility to check the validity of the individual's authorisation. Whether there is a moral obligation on the school is quite another matter.
The Authority's ability to bring matters to a pragmatic solution as described by Whopity will, of course, be severely curtailed after 8 April 2012.