Firstly to Sawman - Many thanks for taking the time to give us your professional opinion and detailed analysis on the construction and load bearing capacity of the building's roof. I for one found it a very useful insight.
Secondly, many people have speculated on the pilot's possible choice of emergency landing site, or that he may have mistakenly thought it was a flat area or a car park etc. if it is to be considered that this was a controlled, or partially controlled forced landing. One thing no one of this opinion appears to have considered is that he knew the area well from having spent over 4 years working at the Glasgow unit based a couple of miles from the crash site. I am sure he spent may an hour hovering over the city centre, in which case he would have known not only the layout of the city intimately, but many of its prominent buildings well also.
I know that when I am tasked to an incident in an area I am familiar with, I firstly consider the immediate surroundings, and often discuss this with my crew before getting airborne, the more experienced of whom are often also very familiar with the incident location and immediate surroundings too.
I think it unlikely that regardless of whether the pilot spent much time in Glasgow when off duty that he would not have known the layout of the buildings in the vicinity of the crash site, adjacent to a major road junction and bridge over the Clyde. Also bear in mind that he had been orbiting around close to this area whilst on task for the previous 2 hours and I am sure would have been spatially aware of his position at all times.