Furthermore, when I did my IR (I've not done the CPL but presume its the same), the CAA examiner told me clearly in the briefing that he would not discuss any of the test sections during the flight. If that was the case for the OP, then he has accepted a verbal contract. That is yet another aspect that may present severe difficulties to him in Court!
Whilst I'm lucky enough to have only done the one CPL skill test, that's my recollection also.
And it's important. I recall in mine becoming slightly uncertain of position because of restrictions put on me by the examiner. I dealt with it, still was uncertain, dealt with it again, and finally worked out exactly where I was and continued to a successful diversion.
The point being that I'd made a mistake, but then recognised it, dealt with it, and got the flight back on track. Had the examiner commented upon or intervened when I initially made my mistake, or even when I got my first attempt to rectify that wrong, I'd have failed the skill test. Because he sat back and watched me, he was also giving me the time and ability to identify and fully rectify my error. Which I'm very glad to say I did, and he considered that to eventually be satisfactory performance.
What appears to me to have been the real issue in the OPs flying was not the incorrect subscale setting - we've all done that from time to time, and many of us have probably done it under test as well. The issue was almost certainly that the OP failed to pick it up and deal with the error in a timely manner, and all the examiner needs to do is say that in court - and the case is over, with the OP out of pocket and a character severely dented by the perception - perhaps accurately - that he showed poor flying, poor monitoring of the flight and inability to correct his own errors, and most damningly of all, an inability to accept and use the corrective opinions of a more experienced pilot.
This last of course is what will render him unemployable, and is the reason why his ONLY sensible course of action is to withdraw his legal action, and write a grovelling letter of apology to the CAA for the misjudgment and wasting of their time. If he's lucky, he then won't end up with a massive bill for the legal fees they've run up already.
G