The Australian Civil Aviation Authority "Flight Instructors Guide" (formerly "publication No. 45") is not too bad for the practicalities of the flying lessons.
It may not be sufficient / adequate for the UK requirements. Can't say for sure on this as I don't have a UK instructor rating!
As for the 'theory of learning' side of things, the FAA "Flight Instructor's Manual" is quite good (I may have the name a bit screwed, but it's very similar).
Any 1st year Uni. psychology text will give you the equivalent of these but without the specific application.
Have fun!
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How surprising! Aircraft use the same laws of aerodynamics all over the world. Has anyone thought to tell the CAA?