Also, going back to the cable trams - will this thread stretch as far as Kennington? (the northern end of the cable tram section - the traditional horses were used between Kennington and either Westminster or Blackfriars Bridge)
If so, the site at 20 Brixton Road, Kennington, is worth a mention.
This was (in cable tram days) a small depot (for one or two trams), stables, and office, as well as housing cable tensioning equipment. (described as having a central arch for the tram, an entrance for horses on one side of the centre, and an entrance for staff on the other)
At electrification, there was an electrical sub-station on the site, which was taken out of use in 1912 when a larger sub-station at Vauxhall was taken into use.
1912 picture on Lambeth 'Landmark' web page
here
Today, the building is an Italian Catholic Mission Centre - Streetview image
here
The history of the LCC tramways lists the sub-station as "20 Brixton Road, Brixton" and does not make any connection with the cable car depot, but I think the 1912 postcard demolishes that.
It is not entirely clear whether the current building was the cable car depot, whether it was a re-construction of it, or was built on the site of it. I can't find any photos of the cable car depot as such (i suppose you can't expect too much for pre-1903) but the written description seems to match the current building fairly well.
The "Cable Restaurant & Snack Bar" at 8 Brixton Road commemorates the operation (when I worked in Kennington in 1986/7 and occasionally lunched there, it seemed to be the unofficial canteen for bus crews on the 3 and 159 routes based at Camberwell garage but having their breaks at Kennington. And the unofficial office for the bus inspector)