Hmm... That went in quite easily, apart from mistakenly choosing S for my missing letter in 16d. But I can only see four unpleasant fellows - three obvious and one middle-theme-worded between 1ac and 12/13 across, which seems clumsy.
Possibly there's an unpleasant fellow in 1ac 4ac (new to me, if so, but plausible), which would make 12/13 a short UF. But then my sense of fair play would suggest the final UF should be in 22/23ac... Are the two UFs I'm missing very obscure?