The problem with the arguments about how the Air Ministry should have backed Whittle earlier is that they rely on the Air Ministry having supernatural amounts of prescience and betting huge amounts of resources on a long shot. As it was, they sent Whittle to Cambridge to further develop his ideas, then seconded him to Power Jets as a serving officer; once it became clear that he had the basis for a practical engine in 1935/36, they greatly increased their funding. Building a successful engine relied on advances in compressor aerodynamics, metallurgy, and combustion that were also useful for existing piston engines; while it's possible a proof of concept gas turbine might have been built a year or two earlier, I don't think a practical engine, never mind a practical aircraft, would have been significantly earlier.