The passenger module had several configurations. In Breakaway, Matter Of Life And Death, Ring Around The Moon, Earthbound & Another Time, Another Place the module had eight seats in two rows. In Black Sun, the rear rows were removed to make storage space. This passenger configuration reappeared in Guardian Of Piri, The Exiles & New Adam, New Eve (with the seats facing backwards). Guardian Of Piri also featured a module with a medical chair and monitors rather than seats.
In Breakaway we see the 8 seat configuration. In front of each pair of seats is an empty storage alcove, and a single screen. Between the seats is a control panel which operates the forward bulkhead screen and communication with the pilot.
In Black Sun, the rear seats are removed for storage space. The red "Emergency Procedure" notice is also seen throughout Alpha and can be read here
In Guardian Of Piri all four seats on one side are removed and replaced with a medical chair and monitors.
In other episodes, the seats are removed to allow boxes to be stored (The Infernal Machine, Mission Of The Darians). This was also done in The Immunity Syndrome, and different desks appear in place of the seating in The Last Sunset and Dragon's Domain
The seat screens are very rarely used- here they are seen in Matter of Life and Death and Missing Link
There is also a "postbox" like slot for papers in the front console of the seats.
Close ups of the seats from Mission Of The Darians
The front part of the seat configuration includes more storage. The cylinders are Gustavberg salad bowls.
In a few episodes, Alphans sleep in the Eagle seats: The Full Circle, The Testament Of Arkadia.
In New Adam, New Eve we see the 8-seat configuration return (although we don't see all the seats). When the Eagle launches at the end, the seats have reversed direction.
Copyright Martin Willey. Thanks to Marcus Lindroos.