Whilst it looks like it could be a small station I doubt that is what it is. A station would more likely be set back from the road, this building is further forward and narrows the pavement. It is also very small for a station in London, it is more appropriate for a commuter village. Surely a long abandoned plan for another rail line into SE23 would have been discussed on here at some point or would otherwise be known about? Would be happy to be proved wrong.

A quick bit of investigation shows that Forest Hill and Catford Bridge stations were both built before the Catford line. Forest Hill station opened in 1839, Catford Bridge in the 1850s and Catford in 1892. I think the south side of Stanstead Road was undeveloped at that point. So this building could have been intended as a station instead of Catford only for the route to be changed. I still doubt it though, why build a station if you're not building the line?

I am now intrigued, hopefully someone knows the history. Interesting that there appear to be painted/covered windows between some of the protruding eaves. These line up with the main windows and entrance. Does the building have a 1st floor or would these ave provided extra light at ground floor level? I haven't been in the bookies.