Apparently, OAP believes that as soon as the Tristars transferred from BA to RAF all the systems magically became something different than they were in civvy service, the APU transformed into a completely different design, and so on.
In reality, other than comma and other military-only systems, I doubt anything was upgraded - much less replaced with different units - thus bcgallacher's extensive experience of civvy Tristars & B747s is about 95% relevant to the Tristars operated by the RAF.
But of course, in the blinkered and self-superior world of certain posters here, that experience is meaningless as it wasn't gained while under a service oath.