The 1919 Housing and Town Planning Act (The Addison Act) is when councils had to come to the fore to supply housing, with a lot of people widely regarding them as 'homes for heroes'.
You had the construction of new suburban ‘garden’ estates, situated on the outskirts of cities. These consisted mainly of 3 bed houses for families and the design of these estates aimed to create self-contained communities of low density. Facilities, including churches, schools and shops, were (supposed to be) provided; pubs were initially excluded! On most of these estates, house were provided with a generous garden to encourage occupants to grow their own vegetables. It took a lot of people out of slum housing.
Where slum housing was demolished newer homes were built so the working class could stay near their roots and places of work.
WW2 then created lots more space between Victorian and Georgian properties, especially across South London, into which a lot of high rise were built, at the time they seemed cutting edge and the answer, hindsight is a wonderful thing though.

I've been following this thread with interest, I've been a resident of Forest Hill for nigh on 20 years and yes the area has 'gentrified' in that time, mainly in a couple of spurts but each time I start to worry that it would lose some of its old character it settles down and doesn't go too far. I'm all for having a butcher and deli's, and use them fairly reguarly but it is nice to keep somewhere like the Bird in Hand where it is cheap and cheerful and is nothing fancy.

As a friend of mine who has lived here all his 40+ years always says, don't worry about Forest Hill, it'll always be all right, after all, this is only Forest Hill.

Do you want no provision of council / social housing in the area, I wasn't sure from your posts?