In my experience (I'm Chair of the Sydenham Society's conservation and planning committee) a conversion such as the one that was going on at Church Rise should have had planning permission before the second lot of work started, and the developer should have displayed the yellow notice way before planning permission was given; in addition, neighbours should have received letters of consultation so that they could object. Of course some developers start work and then apply retrospectively - in a sense, the Council relies on neignbours and amenity societies (the Sydenham Society and the Forest Hill Society) to be its 'eyes and ears'. Re any subsequent development - there is no guarantee of a 'like for like' building unless Church Rise is in a conservation area (and even then this is not guaranteed, as planners and architects are not keen on a 'pastiche' approach, largely because the building materials, techniques and craftsmanship available to the Victorians and Edwardians is either not available or too expensive for today's developers / house builders). As has been explored on SE23.com on other threads, there has been a call for more conservation areas in SE23 - the best approach is to join the Forest Hill Society and get them involved (if you are not already a member).