I recently found thisvideo online. It is another tour by a news company similar to the BBC tour several years ago. What is most interesting about this tour is what can be seen from 2:00. A large space never previously seen in any Youtube video (too my knowledge). The space is filled with editors, artists and also all the awards and fan items from the old common room before Hat Films moved in. Further, Turps says "This is actually where the magic happens, downstairs" - in reference to the corridor of offices we are used to seeing. This is clear evidence of what was rumoured, Yogtowers definitely has expanded to other floors.
Other examples of the Yogtowers expansion can be seen in the Christmas Vlogs (I haven't got a link, there on the main channel somewhere) The vlog videos seemed to show a new, smaller common room. This too could be on the second floor of YogTowers.
This was just and interesting video I found that confirmed some previous guess work I made whilst watching some YogTours videos, please tell me what you think!