Door size
If you look at Bury's print of Crown Street station, you are immediately struck by how small the people are standing on the verandah. Bury was an architecture student, so maybe he wanted to accentuate the grandeur of the built environment or possibly that's what his publisher, Ackermann, needed to attract custom. Another possibility is that the men in the picture are actually smaller than we expect (average male height would be about 5ft 5 in in the early 19th century) and that the door was significantly bigger than the average front door enountered these days.
Figure: Bury's print of Liverpool Crown Street station with inset showing paired pilasters (left, Wikipedia) and the former main door at Sudley showing paired pilasters and suggested size of original main door (red outline).
If the hypothesis is correct that both Sudley House and Crown Street were designed by the same architect, JW Casson, then perhaps the main door at Sudley served as a model for the station. As previously mentioned, both have paired pilasters with sidelights.
My guess is that the main door at Sudley originally filled the space presently occupied by the door, small sidelights and transom light. That would equate with the door at Crown Street which lacks those features and, very rough guess, would make the door plus immediate surround about 5ft wide by 10 feet high. If the door to the platform had similar dimensions then it is not that the men pictured next to it are small but that the door is just larger than expected.
A door of that size had practical consequences. It meant that two people could pass each other going in opposite directions and that awkwardly shaped luggage or packages could enter without difficulty. In all probability the door was also a status symbol. Its size would impress and in a house the owner would employ someone whose job in part was to open it for visitors.
The missing door knob
There are two contemporary pictures of Crown Street that show the door, one by Bury and one by an unknown artist that appeared in 1833 in the Penny Magazine of the Society for the Distribution of Useful Knowledge. The latter looks like Bury's print minus coaches, carriages and people. However, it also shows features of the train shed/verandah missing from Bury's print but present in Shaw's sketch in which the door, alas, is obscured by omnibuses. Neither shows a door knob or handle. While it is possible that this omission was made on aesthetic grounds or that the knob is hidden by the door recess, another possibility exists: there was no door knob.
Perhaps the wealthy first class passengers expected to have doors opened for them. The station clerks would keep an eye open through the sidelights for the arrival of the coaches and open the door from the inside when one arrived. As each coach reversed up to the door, the 18 passengers would get out and queue through the door to the desk inside as they checked-in, their names being added to the waybill given to the train guard. The portico/porch would shelter them from rain or bright sun depending on the prevailing weather. They would then proceed either to the waiting-room beyond or onto the verandah.
The door is not seen as opened in Bury's print as the people have just arrived from Manchester and are boarding the omnibuses. Their carriages have been marshalled for the next departure.
The booking office(s)
Clearly the clerks would not want to open the door for each and every visitor so the door on the verandah would be the normal entrance for those wanting to make a booking in advance (as was required). Generally such booking would be transacted via the Dale Street office in the city centre but Crown Street would be more convenient for those living in country houses as many merchants and bankers did. It is not unlikely that such bookings would be made by servants used to using a secondary entrance.
The spatial separation between departure and booking traffic suggests that the second door further along the verandah would be for those using second class trains. This is something I had considered previously but abandoned. While not ideal, it makes more sense if both classes accessed their respective booking desk via the verandah rather than first class passengers having to wrestle with the huge door. Again second class passengers would queue sheltered by the verandah. It would be a little less convenient with the same door being used for passage in both directions but that was probably the idea.
The doors at Manchester and Sudley
Of course, a plausible solution to the door mystery doesn't absolve Bury of all errors of perspective but it perhaps explains the smaller double-doors and larger check-in area at Manchester. As a consequence Manchester didn't require a porch and, according to Fitzgerald, sported a vestibule to retain some wamth from its coal fire in wintertime. Some of this may reflect different local circumstances but it may also be a consequence of a more custom, less off-the-shelf, approach to the Manchester design. If so, this constitutes further evidence that Crown Street was built prior to Manchester and informed its development.
For some reason the second family to occupy Sudley, the Holts, changed the main axis of the house such that the entrance moved from the side considered here, the east, to the north side of the house. One possibility is improved access for carriages but another might be the considerable loss of heat that occurred when the large east door was opened in cold weather. The extensions to the wings along with the portico would have provided some shelter but not as much as the curious blind-ended portico ultimately added to the north.