I don't think they can be "Corbett" houses, Roz. There is a fairly detailed study of his work and it makes no mention of houses in Forest Hill. A. Cameron Corbett (as he's usually known) was a builder between 1877 and 1914, building all but two of his estates north of the Thames, mostly in Essex. His estates were large, in the region of 100 acres each. South of the river there are just two recorded, at Hither Green and Eltham.