Rickye, as you say, there are only a limited number of likely places for the 13 connected cells. If it were the the right hand file, there would be no need to 'fold' - it could just be cut off. If it were the bottom row, then a fold might conflict with the area below the grid. So, the centre file may as well have been lit by neon. If you've solved the 2 penultimate Group A clues, you can probably get them in straightaway (though be prepared for an inconsistency); the rest follows quite easily.
Dryden, I agree. I was expecting something more (eg. using lines 7 & 8 of the stanza) - though if I'd read the preamble properly I would have known not to look further than line 5. In abstraction from the puzzle, a nice verse and a lot more from the same source is well worth reading.