Reading up on toilets and stairs

i started by reading the accessibility code of bca. it started with a typical design problem of finding an approx length of stair needed for a given floor to floor height. it seems though that length can be found, for width probably a (1+1+0.2 ) 200mm could be a spacing or if structural wall could be a full brick with plastering. sizing of bricks can be found below:

http://www.bricktiles.com/products/claybrick_clayblock.html

For F-F of X: approx length Y (including wall thickness)

 3000mm - 6500mm
 3200mm-  7000mm
 3600mm-  7300mm