Unfortunately my file for the Thicket Road numbers spreadsheet I created several years ago has got corrupted, so I've had to redo at least the bit around No 78. It was, indeed, called Sunninghill and originally No 9, which changed to 78 between directories of 1876 and 1880. I haven't found another renumbering, but I've only got to 1967 so far. Perhaps it was the other side I thought changed more than once.
Stanford's 1862 map show no houses at all in what was then called Thick Wood Road. The earliest following directory I have is 1867, which shows Mrs Hennings as the resident, so I guess she bought it as a new build. I wouldn't be surprised to find an advert in The Times for whatever the term then was for a "des res" with view over the Crystal Palace grounds. Houses were sometimes named by the builder, but as some of the others only had numbers, I suspect Mary chose Sunninghill which might have had some personal significance.
I'll get a photo of the modern 78 when I'm sure that's still the right number. I'm told that West Norwood Cemetery has now been re-opened (despite the forbidding wording still on the Council website) and the person I mentioned is going to look for the grave.
More to come.