Watch Office additions

Which watch office?

It would have to be the first or second floor extension as 7345/41 is the ground floor type 'B' structure. As the observation room 13079/41 is not mentioned it could be something similar to that or the Seco signalling pent house that was erected at second floor level. Equally though drawing 13079/41 might simply have been omitted from the RSP even though it had one and the Works Area 15 drawing is the extension to it, to create a control room. Confused? I think it makes sense.