Perhaps these people at LAARC can help you - worth a try? http://www.museumoflondon.org.uk/English/Collections/ArchaeologicalResources/ArchaeologicalArchive/
If you choose 'online resources' and click on 'go to the online catalogue', and search for 'kensington', it comes up with a list - could it be the John Atkins building? Whichever - looks like an interesting resource which I wasn't aware of before..