I don't know if this is of any help to you, or if this is the list you've been trying to narrow down, but the
ABRSM Diplomas Reading List might be a good place to start if you've not already seen it. I'm sure people will have personal recommendations of which books they've liked which will be more helpful, I suspect extending your questions to which books people have found helpful in teaching generally would get more responses (there aren't that many people here who have done the teaching dip but there are a lot of experienced teachers) and books relavant to good teaching I'm sure would be helpful in the viva too

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