Let me remind you...
asking an expert is a proper answer.
As what *you* quoted says, its an MOT failure. It doesn't become un-roadworthy if it fails an MOT it already is. It becomes documented as un-roadworthy when it fails. Will a copper do you for it? well ask them. While you are at it ask your insurance what the cover is on an MOT failed vehicle, I would be interested to know what different companies say.