At the risk of being seen to "rise to the bait" there are some totally unfounded and plain wrong "facts" being bandied about. Some people are impressionable whilst others seem to have nothing but malice. It requires rational explanation and then let it die please.
1. The Obstacle treatment applicable to Cat I, CatII and Cat III ILS's is identical with respect to the Transitional Surface and the Inner Horizontal Surface. There is a slight difference between the Baulked Landing Surface (BLS) within the Obstacle Free Zone. This starts 900m beyond the landing threshold and splays at 10%. It will therefore be apparent that any obstacle (building) at any airport which permits Cat I operation will permit Cat II or III operation also. The building so freely attributed to be "an Obstruction" is also outside the BLS being, as it is, only 750m from the landing threshold.
But of course any air traffic controller or professional pilot would know this, or know where to find it (CAP 168 Chapter 4 paras 4,5,8,9)
2. Where this Cat II discussion started is anybodies guess, but Humberside is just one of 26 "Airports" within the UK with a Cat I ILS only. Of the others at least 11 could be argued to have more Commercial passenger carrying movements. These include Aberdeen, Bournemouth, Cardiff, Coventry, Doncaster, Durham, IOM, London City, Jersey, Norwich, Prestwick and Southampton. Not many of these would be actively contemplating the installation of Cat II ILS. It is driven by a very high number of diversions, it is not the presence (or absence) of ILS Cat II that attracts traffic.