Diesel-electric machinery removes petrol from a dangerous hull

How likely was the Royal Navy to abandon petrol-electric submarines after the D and E classes?

Very likely, because diesel-electric machinery was better and reduced the amount of combustible material inside the submarine.

The service already understood that diesel-electric propulsion was superior. A submarine is an especially dangerous place to carry avoidable combustible fuel. Moving away from petrol therefore improves both machinery choice and basic survivability. The transition was likely even without one particular accident forcing the decision.