According to this, rather nifty, website, the Perry Vale road closure is due to gas main replacement on Perry Vale and Waldram Park Road/Crescent/Place. It also says there will be temporary traffic signals, Perry Vale will be closed eastbound and Stanstead Road will be closed (I assume this means the residential part of Stanstead Road, not the South Circular part).
Is the 356 bus diverted in both directions? I know the Upper Sydenham-bound bus is going down Church Vale but I don't know if it's also diverted in the opposite direction. The bus stop outside All Inn One didn't have a 'not in use' sign on it last night and a couple of people were waiting there for the bus.