There are two main types of dual controls for driving school cars. Cable operated and rod operated. Cable operated duals seem to be becoming more prevalent. Ana dvantage of rod operated dual controls is that you can have them set up either to work independently of the main pedals or in tandem with them. Some instructors like rod operated dual controls that where the instructors pedal moves at the same time as the pupils. The danger is that if you are not careful you can get your foot trapped under the pedal when the pupil operates the pedals!
The main supplier of dual controls in the UK is He-Man. HeMan are based in Southampton but have agents throughout the country. You can get a comprehensive list of Heman Dual Control fitters here.
Another supplier of Dual Controls, based in London, are Bestway.
