Humbrol Ltd were making paints for Modellers since the 1950's 
And were one of the leading manufacturer of model paints in the UK. 
Their range of paints was one of the most complete for all Model types 

Airfix Skill Levels 
All Airfix Models displayed a skill level on the packaging along with sizes
And recomended Colours for the kit.
The levels ranged from 1 (for beginners) to 4 (for the accomplished modeller).

Series 1 to 20 determined the level of skill and size on the upper end.

Starter Kits were the best value as these were supplied with everything 
A Modeller would need to assemble and paint their kit.
The Price Range was from A to D with the level of skill at the upper end.

The shop stocked a wide range of Starter Kits, Paints and Airfix latest 
Promotions - Special Orders were supplied if available in the 2006 Book
Due to the recent take over by Hornby we still await further Info as to the
future of its past models I would strongly urge collectors of the AIRFIX
brand to stock up on available stock as this may prove very collectable.