I've just read the story and thoroughly enjoyed it. It reminded me of my own early days in the motor trade, just after I left school and worked for the next five years in an engine reconditioning company. It was started by the son of a wartime petrol tanker driver, who'd made his fortune selling black market petrol. He financed the company when it started up, and remained as overall main shareholder until he died, which was not long before I left to go into general engineering.
However, the characters you described were definitely indicative of the people I met in the trade. The word 'straight' didn't figure in their language, and if they could fiddle an extra bob or two out of the customer then all well and good.
Thank you for bringing back a long lost memory of a time now fading into history, that will for many evoke a response of 'good riddance!' but which for me recreates something real, that I can recall with a certain fondness.