This is an extension of the two way switch wiring.
The top switch wiring is unchanged - two cores from the ceiling rose, and one end of the three core cable.
The middle switch has four terminals, and must be an intermediate switch. Two of the wires are cut and connected to the switch. The third wire (connecting the COM terminals of the other two switches) is linked in a separate terminal.
The bottom switch wiring is unchanged - the three wires connect to the three switch terminals as with the two way arrangement.
All of the earth wires connect to a terminal in the backbox, or alternatively to a separate earth connector.
This arrangement can be extended to four, five or even more switches. All of the additional switches must be intermediate types, and are connected in exactly the same way as the middle switch shown here. The light can be turned on and off from any of the switches.
Red = Brown
Black = Blue
Red = Brown
Blue = Black
Yellow = Grey
Not many people. Intermediate switches are uncommon, and there are very few situations where three or more switches are needed.
Switching all of the lights simultaneously in a multiple floor stairway is not a good idea - what if other people are using the stairs but you can't see them?
Finally, for a large spiral staircase, just get a ceiling mounted pull cord switch and attatch an extra long cord, so it can be reached from any point on the stairs.