I've just spent an enjoyable half hour reading the thread on Sheffield Forum ... come on Rootschatters - let's see if we can sort this one out!
For my money, the letters are 'C' and 'R' (the two circles in a 'B' would, I think, be of more equal weight, but I think this shows a smaller circle for the top, and I'm not convinced the 'circle' on the bottom is a full one).
Like dave the tyke, I'm heading in the direction of a railway hotel.This site
suggests there was a Great Central Railway that connected Sheffield with Manchester and Lincolnshire.
Could this, therefore, be a hotel for the C
There's what looks like a shop on the left hand corner, and then an archway that looks awfully like it might be an entrance into a booking hall, with either posters or booking counters lit up inside.
Am I barking up a wild goose here?