I don't teach Performance, but I was wondering if anyone had considered a formal complaint to the CAA about the nature of the exam? It would be hard to do through the schools, as the instructors do not see the exam, they can't complain by direct experience, and there is a fairly strict procedure that only allows restricted grounds for complaint. It can be brought up at the next CGIs' meeting, but I as a humble subject instructor don't know if anything else can be done.
On the other hand you guys paid £55 each to be in that exam hall. You are the customer, and the CAA examiners are very clearly not doing the job they should be doing. You have been ill-served, and for some it may cost you a fair amount of money - a couple of months living without earning in some cases, i.e. thousands of pounds in delays to career. The CAA should be made to understand this, as some of them have never been in the situation and tend not to understand the reality of flight training from the student's point of view.
Who knows, maybe even the sale of goods act applies, as you have paid for a service.