Information extracted from the Johnsons of Hendon Ltd advertisement in the 1949 BJPA, p39.

Ian Grant e-mailed to say "I bought a 1949 BJP Almanac ........... in it there's an advert for Johnsons ColourForm, a colour developer/colour coupler system for toning etc.
Tetenal later sold something similar in the UK in the 1980's & 1990's.
The advert said "Write for an Illustrated booklet", and guess what - the book's owner had, and tucked it inside. I've scanned the booklet for you. (To download this booklet as a pdf file, click the image alongside or here).

Ian adds "I've used the same process but from raw chemicals and Bob Carlos Clarke used the Tetenal version for many of the images in (his 1985 book) The Dark  Summer".

An article on Using Colourform, from 'Practical Photography' magazine, July 1962, can be downloaded here.