The MOT test on the brakes is only a visual inspection of the components and a very simple brake efficiency and balance test. The warning light you have is probably for your pads reaching the end of their life, the brakes will easily pass an MOT with them in this condition.
Please check that the warning light is not low brake fluid level, you really don't want to be driving it in that condition
if you really want to know if the tester should have told you wade through this lot
MOT UK car and vehicle MOT information equipment car servicing parts and spares - testers manual (it may not be up todate).
I am surprised the tester didn't say anything to you because in my experience they are a pretty thorough lot and will normal point out lots of things which may not be a failure but are useful to know.
seeya
Don't forget cars are for crashing, fixing and thrashing!