Following recent EU directives, the penetration of smart sustainable buildings (SSBs) in low voltage (LV) networks is expected to drastically increase. This open ups opportunities for developing novel frameworks to coordinate the provision of ancillary services (AS) stemming from SSBs. In pursuit of investigating the extent of the previously untapped potential of LV networks, this work proposes, for the first time, the development of an SSB-driven MV-LV coordination framework for the provision of AS, inspired by industrial HV-MV AS schemes from the European landscape. Analytical formulations of passive and active ancillary schemes are first presented, in the form of mixed-integer nonlinear programming problems. Analytical reformulations and approximations are then proposed, to derive computationally lighter mixed-integer linear programming models. The real-time management of AS provision is based on a novel 3-stage, model predictive control approach, driven by the collaboration between distribution system operator and SSBs, the latter considering environmental and phase balancing aspects in their optimizations. Emergency situations with network violations are also considered. The approach is validated, tested, and compared to its predecessor, i.e., its past, cruder version, on a multi-feeder LV network containing different types of SSBs.