Going back and forth between Smyth (#2742 ...) and Cooper has me somewhat confused concerning μὴ οὐ + inf after negative verbs. When used after negative (or negatived) verbs, μὴ οὐ is not a "double negative" in the English sense. According to Guy Cooper (v.2 page 1128, #67.12.7) μὴ confirms the negation (semantic) inherent in the verb the addition of οὐ doesn't appear to alter the sense.
Example:
Sophocles Trag., Ajax
540 {ΑΙ.} Τί δῆτα μέλλει μὴ οὐ παρουσίαν ἔχειν;
"Why is his arrival delayed?" The negative sense of μέλλει (not yet ...) is reinforced by by μὴ οὐ ... παρουσίαν ἔχειν (to have arrived). Eliminating οὐ doesn't alter the meaning.
C. Stirling Bartholomew

