I did that all those years ago. However, after both the garage and the M.O.T. people initially agreeing that my car should have passed the test, they closed ranks and started the ahh but this, and ahh but that routine.
Eventually, as my mum needed an M.O.T. I took it to another place, pointed out the "supposed fail" which they agreed was ok so I submitted it to the test which it passed.
So, it seems that a tester can make decisions outside their remit.
It's like a lot of things. There will always be people who talk absolute cobblers with great conviction. However, I'm with Mottie on this one. I don't mind playing by the rules, as long as everyone does it. Generally, I like everything on my car to work, so even though the reverse lights aren't an MOT fail at the age mine is, I fixed them. However, if I hadn't had a reversing light switch "on the shelf", so to speak, I wouldn't have wanted the car to fail, because the chances of me getting another one (it's a rare car) within the 7 days for a free retest, would have been slim. It would have been much more convenient for me to fix it at my leisure, so I'd probably have threatened to appeal if they'd tried to fail me, had they not been working. (Assuming that was the only fail point, of course)!