Just to help here is the ABE URL for the search I just did and below it is the same search narrowed to Australian stockists
Kind Regards to you and gratitude to your Dad for his service
John
Melbourne
PS I have bought books from the Australian stockist, Andrew Barnes and had no trouble.
AbeBooks: Search Results - Martin Middlebrook and Bomber Command War Diaries
AbeBooks: Search Results - Martin Middlebrook and Bomber Command War Diaries