Now with something like a 747 for example, if the METAR at your destination is showing that the cloud base is 200ft, would you still manually attempt an ILS approach and land if visible by 200ft or go around if not
In principle, you are correct, in so far as that you would 'go around' if not visual at 200ft. However, in my company, the reported ceiling is not the controlling factor. The reported visibility or RVR are the controlling factors for any type of ILS approach, so you would not be wrong to descend to 200 feet and then go around if not visual.
Experience, and good airmanship though, would suggest, as you do, that you prepare at least for a CatII approach in those circumstances. Saves all the extra fuel and ASR's from going around.