I believe that headlamps pointing down too much, as well as up too much, can be an MoT failure. If you have left your switch in the wrong position you might find it has failed but, any garage wanting return custom would re-think if you pointed out to them what the problem was.
I once had a car fail its MoT because the ABS warning light was on. I pointed out that the car didn't have ABS and that I'd used the warning light for something else, so they just changed the "fail" to "pass".
I'm not sure Joko's argument is valid - there are lots of controls on a car that you can use to break the law; accelerator, fog light switch, horn etc. It's down to the driver to be in control of the car and use it legally.