MHCLG and its predecessor DCLG publicly publish accounts and financial statements going back to 2010/11 which can be accessed here: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/247455/0971.pdf.
The overall investment in the 2008-11 National Affordable Housing Programme (NAHP) was £8 billion at the start of the programme, with a further £2.28 billion allocated to the programme for residual delivery in the 2011-15 Affordable Homes Programme (AHP) for a total of just over £10 billion.
Details of these amounts may be found at:
To provide data regarding the annual amount of grant funding allocated to affordable housing by the department in 2008/9 and 2009/10 internally would be at a disproportionate cost to the department. However, this data may also be found in the public domain at: https://www.gov.uk/government/collections/hmt-oscar-publishing-from-the-database.