Engines: the brochure to attract A.M funding has a sketch, weights, performance projections. A.M Requirements staff see an application to a similarly origami-ed airframe sketch and extract funds from Treasury. The ITP states a target date for A.M Type Test: 100hr. bench run over the intended operational envelope. That requires some, not all, of the accessories that will in Service comprise the installed power egg. They are, mostly, separately contracted by A.M with vendors (we speak of magnetos, carbs., props.) Cue: mess.
Then add chopping and changing of political perceptions of Threat; add the need to move general engineering industry from civil/export work into munitions, in order to actually build things (UK Aero industry was not a mass production sector)…and you suspect that some of the Hendon New Types displays were intended to achieve their deterrent effect without ever being deployed.

So, if your intent is to try to measure that, say RR complied with schedules better than/worse than, say Napier…then good luck to you. Example: conventional wisdom is that Morris was incapable of producing Spitfires from CBAF, so Vickers was given the job and delivered within weeks. So they did…of near-complete airframes trucked in from Eastleigh.