There are only two types of taxi, in reality only one has the majority. Hence one supplier, one parts supply:
"Two production vehicle models comply with the current conditions: the London Taxi Company TX4 and a specially-modified taxi variant of the Mercedes-Benz Vito with steerable rear wheels"
There are only 6 testing stations, all run by one company NSL, and taxis have to pass two tests a year at them:
https://www.quotax.net/new-taxi-inspection-centres-addresses/
Taxis can only use authorised spare parts from the former in order to pass the latter. Though you can take it to "any repair shop" in theory, the parts, end-result and testing are still under monopoly control, effectively.
Biting the hand that feeds IT
