I forgot you mentioned 11 A - the first half is ?i?...
I still don't know where 'favelas' comes in, hadn't thought of the workhouses options.
18 D turned out to be a fairlly innocuous word - s(sons) + a synonym for 'tumble about' The definition was 'feel faint' but I used the word, as a verb with 'ing' as meaning 'very hot' weatherwise. Don't know if any of this helps!