Hi, I know this is an old link, but I have copies of the station plans for the City & South London Moorgate station, so I'll Explain them through to you.
The PLatforms Go North to South, from 12 oclock (North) to 6 oclock (South). At the far end (6 oclock) there is a passage (Which I shall call AA), which used to be a platform cross passage that leads, via stairs to a spiral staircase from the booking hall (which are not original) The spiral stairs begin on the right hand side, on the left hand side is a door, which behind this is the passageway that leads to the lifts (This originally was the one from lifts to platforms.) The passageway curves around to 7 oclock with a 1 in 10 incline and has an entrance Which I shall call BB) to the original sprial staircase on the right hand side (I'll get back to this later). The first photograph on the abandoned stations site is therefore taken just after this staircase entrance heading towards the lifts. In the picture, the passage curves again at the end, which is a curve to 9 oclock where the exit to the lifts are on the right hand side. The second photo shows one of the two lift shafts. Therefore going to the other side, the entrance to the lifts are in my right and the passageway follows the same direction from 9 oclock, but has a sharper curve just a little bit further along (at this curve, the passageway from the spiral staircase joins on the right hand side, which I shall call CC) and the curve is about half 7 oclock. This is where you find the 3rd picture on the site as being sealed off. This passage remains at level and effectively curves to 6 oclock above the other passage at the cross passage (AA). This passage then begines to decline at a 1 in 10, headin parallel to the platform (Going to 12 oclock) , then decends 18 steps. The entrance is in a cross passageway, where the more modern stairs for the exit to the escalator are, once you desend the modern steps you see a white a modern white tiled wall, turn left for Morden, Right for Euston. Behind this tiled wall is the 18 steps and sealed passageway.
Back to the spiral stairs, because BB exit passage is on a incline and CC entrance passage is level, BB exit passage has 6 steps to bring it level with the CC cross passage. The stairs then are on BB left and CC right, which is a 25 stair passage which then leads to the spiral staircase (situated above the curve of the lift passage exit)
Grab a pen and lets us know how you got on !