The message
from Brian Robertson contains these words:

Other than that, try http://www.signalbox.org/ I think it is a tall
order hoping to find out how many levers the boxes had though.

The Signalling Record Society publish a series of books (obtainable from
the usual suppliers), each book covering a section of main line and its
branches. There is one for the Brighton main line, IIRC, and they list
all the signal boxes along the line, including the alterations made over
time, and show the track diagrams for each box, and the number of
levers. I have the various volumes which cover my areas of interest:
LNWR, L&Y, NS, CLC etc., and they make fascinating reading.

--
Dave,
Frodsham