Here's further information from council meeting minutes (housing) Sept 15 that they didn't include in their letter to residents:

Eliot Bank, Forest Hill (48 homes)
7.18. The proposal is to build 45 flats (11 x 1-Bed and 34 x 2-Bed) and 3 houses (3 x 3-Bed) across three sites on the Forest Estate. The current proposal is for the delivery of 22 homes for Social Rent and 26 homes for private sale. The scheme is formed from underused open-space, garages and a parking area that is proposed to be relocated. New housing proposals will be complemented by environmental improvements to the remainder of the existing estate.

7.19. The site is in close proximity to the Hanover Housing Association development at Featherstone Lodge which, obtained planning consent for 33 new homes in April 2015. It will be necessary to manage the construction programme accordingly, and it may be necessary to delay the start on site to allow for the completion of works at Featherstone Lodge. It is expected that consultation with residents and ward councillors will commence in the autumn.