Lots of really clever clues in this one, especially 25ac and 7dn! The unclued entry is the key to what's going on. For those answers that seem too long, just note that they all cross that central vertical. That's as much of a helping hand as I'm going to offer.
What I can't fathom is how the 'pairs of letters ... provide' examples. I've written out all the possibilities but all I have is gobbledygook.