We will!
Ignoring complications like junctions and even bigger complications like four running lines, a typical double line box would have from the left with lever no.1:
Distant, home/starting signals in order, points/FPL/shunt signals, starting/home signals, distant signal.
FPLs would be adjacent to the relevant point lever (without checking diagrams I can't say whether one side was usual)
The two shunt signals reading through a crossover would be either side of the point lever.
Your layout seems to be actual Aberaeron, so is simpler than above. The lever numbers can just be made out on the SRS website http://www.s-r-s.org.uk/html/gwm/S2106.htm. It is a very small and efficient frame. No yellow levers (no Up distant, Down is fixed), 3 and 4 are crossovers, 5 is FPL for 4, 6 is Down Home, 2 is Up Starting, 1 is Up Home OR sidings to main shunt signal. There is no signal protecting the exit from the headshunt/engine shed and I can't see what operates the shunt signal for the run round move. (It may be a point indicator worked with the points, not sure if GW had those.). You will also need a token/staff instrument in the box.
There are other threads on GW signal box interiors that you should be able to find by searching, including a very informative one by Mike (Stationmaster) himself. He operated and managed such boxes, I'm just the engineer who didn't write enough down when younger as I didn't know I would need it to help others with their modelling!
Paul.