I think you are confusing conventional care with the preventative role of the regulator.
The NHS exists to treat symptoms (plus a smattering of screening). If you are ill they provide treatment but they dont provide significant consultations or investigations purely because of a possible risk. You have provided no details but there are many instances, for example of a slightly abnormal ECG, that would not warrant conventional NHS intervention but might indicate an increased risk of incapacitation. The recommended manangement after a heart attack is not the same as the investigations the CAA will require, but they do so as they need to ensure the risk of incapacitation is minimal, whereas the NHS merely checks there is nothing that needs drugs or operations.
As it isnt NHS you have to pay. But each doctor sets his own fees, and the referrer gets no payment for referring you so I dont know what you are insinuating. The CAA decides the tests not the AME.
Still dont follow the argument about Magistrates. Any hearing would involve court costs, the costs of medical experts on both sides, the necessity of appeal to a higher court etc etc. Anyone who has been up against the CAA knows they have a bottomless purse. If you are worried about the financial costs of having your medical pulled I suggest you consider the legal costs of going to law. And the rest of us would also pay in higher fees