As far as I remember, and as you know I follow Harry's comings and goings quite closely, he has only had two homes in the KP complex in his adult life. One was that tiny one bedroom apartment, ex staff quarters, that he occupied at the time the Cambridges were at Nott Cott. The other has been the two bedroom Nott Cott which he moved into shortly after the Cambridges moved out. Where would he have moved to? Most of the rooms at KP are used for other purposes, and there aren't spare apartments just lying around for the taking.