I think there is only one possible answer for 42a if the puzzle's title is a hint, but for 45a there seem to be three options so like you I have gone for the 'Navajo' one as it's the most familiar.
Gourami,
Think of “It” as a two letter code. I note the abbreviated “little land” is in Collins but not Chambers.
Some UK-specific GK required for the rest.
I had two answers that were consistent with the title - one a small town in the borough of Bexley and a hyphenated one of non-English origin.
I've gone with the former.